diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 64dff583..768fe615 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -20,9 +20,7 @@ jobs:
 
     strategy:
       matrix:
-        php: ['5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3']
-
-    continue-on-error: ${{ matrix.php == '8.3' }}
+        php: ['7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4']
 
     name: "Lint: PHP ${{ matrix.php }}"
 
@@ -40,31 +38,11 @@ jobs:
       - name: 'Composer: remove PHPUnit (not needed for lint)'
         run: composer remove phpunit/phpunit --no-update --no-interaction
 
-      # Install dependencies and handle caching in one go.
-      # @link https://github.com/marketplace/actions/install-composer-dependencies
       - name: Install Composer dependencies - normal
-        if: matrix.php != '8.3'
-        uses: "ramsey/composer-install@v2"
-        with:
-          # Bust the cache at least once a month - output format: YYYY-MM.
-          custom-cache-suffix: $(date -u "+%Y-%m")
-
-      - name: Install Composer dependencies - ignore PHP restrictions
-        if: matrix.php == '8.3'
         uses: "ramsey/composer-install@v2"
         with:
-          composer-options: --ignore-platform-req=php+
           # Bust the cache at least once a month - output format: YYYY-MM.
           custom-cache-suffix: $(date -u "+%Y-%m")
 
-      - name: "Lint PHP files against parse errors - PHP < 7.0"
-        if: ${{ matrix.php < 7.0 }}
-        run: composer lint-lt70
-
-      - name: "Lint PHP files against parse errors - PHP 7.x"
-        if: ${{ startsWith( matrix.php, '7' ) }}
-        run: composer lint7
-
-      - name: "Lint PHP files against parse errors - PHP >= 8.0"
-        if: ${{ matrix.php >= 8.0 }}
-        run: composer lint-gte80
+      - name: "Lint PHP files against parse errors"
+        run: composer lint
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 3e439c55..9c95e319 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -5,14 +5,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        php: ['7.2', '7.3', '7.4']
-        phpunit: ['6.3.1']
-        wordpress: ['6.0', 'trunk']
-
         include:
-          - php: '5.6'
-            phpunit: '5.7.21'
-            wordpress: '6.0'
           - php: '7.2'
             phpunit: '6.3.1'
             wordpress: '6.0'
@@ -29,10 +22,16 @@ jobs:
             phpunit: '8.5.16'
             wordpress: 'trunk'
           - php: '8.1'
-            phpunit: '9.5.27'
+            phpunit: '9.6.21'
             wordpress: 'trunk'
           - php: '8.2'
-            phpunit: '9.5.27'
+            phpunit: '9.6.21'
+            wordpress: 'trunk'
+          - php: '8.3'
+            phpunit: '9.6.21'
+            wordpress: 'trunk'
+          - php: '8.4'
+            phpunit: '9.6.21'
             wordpress: 'trunk'
 
     services:
@@ -84,18 +83,6 @@ jobs:
         with:
           composer-options: --ignore-platform-reqs
 
-      - name: "Lint PHP files against parse errors - PHP < 7.0"
-        if: ${{ matrix.phpunit == 'auto' && matrix.php < 7.0 }}
-        run: composer lint-lt70
-
-      - name: "Lint PHP files against parse errors - PHP 7.x"
-        if: ${{ matrix.phpunit == 'auto' && startsWith( matrix.php, '7' ) }}
-        run: composer lint7
-
-      - name: "Lint PHP files against parse errors - PHP >= 8.0"
-        if: ${{ matrix.phpunit == 'auto' && matrix.php >= 8.0 }}
-        run: composer lint-gte80
-
       # Scan the logs for failing tests and surface that information by creating annotations and log file decorations.
       - name: Setup problem matcher to provide annotations for PHPUnit test errors and failures
         # The JSON file is provided by the `shivammathur/setup-php` action. See https://github.com/shivammathur/setup-php#problem-matchers.
diff --git a/README.md b/README.md
index 2ed25e87..0d8e4c8d 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 - Contributors: akirk
 - Tags: friends, rss, decentralized, social-network, own-your-data
-- Requires at least: 5.0
+- Requires PHP: 7.2
 - Tested up to: 6.7
 - License: GPL-2.0-or-later
 - Stable tag: 3.2.1
diff --git a/composer.json b/composer.json
index 9b8deda1..fbbaa03e 100644
--- a/composer.json
+++ b/composer.json
@@ -17,13 +17,7 @@
 	},
 	"prefer-stable": true,
 	"scripts": {
-		"lint7": [
-			"@php ./vendor/php-parallel-lint/php-parallel-lint/parallel-lint . -e php --exclude vendor --exclude .git"
-		],
-		"lint-lt70": [
-			"@php ./vendor/php-parallel-lint/php-parallel-lint/parallel-lint . -e php --exclude vendor --exclude .git"
-		],
-		"lint-gte80": [
+		"lint": [
 			"@php ./vendor/php-parallel-lint/php-parallel-lint/parallel-lint . -e php --exclude vendor --exclude .git"
 		],
 		"check-cs": [
diff --git a/feed-parsers/class-feed-parser-json-feed.php b/feed-parsers/class-feed-parser-json-feed.php
index 382025a1..acbc8294 100644
--- a/feed-parsers/class-feed-parser-json-feed.php
+++ b/feed-parsers/class-feed-parser-json-feed.php
@@ -116,7 +116,7 @@ public function discover_available_feeds( $content, $url ) {
 	 *
 	 * @return     array            An array of feed items.
 	 */
-	public function fetch_feed( $url, User_Feed $user_feed = null ) {
+	public function fetch_feed( $url, ?User_Feed $user_feed = null ) {
 		$args = array();
 		$res = wp_safe_remote_request( $url, $args );
 
diff --git a/feed-parsers/class-feed-parser-microformats.php b/feed-parsers/class-feed-parser-microformats.php
index 6a758e80..40b5f336 100644
--- a/feed-parsers/class-feed-parser-microformats.php
+++ b/feed-parsers/class-feed-parser-microformats.php
@@ -337,7 +337,7 @@ public function parse_hfeed( $mf ) {
 	 *
 	 * @return     array            An array of feed items.
 	 */
-	public function fetch_feed( $url, User_Feed $user_feed = null ) {
+	public function fetch_feed( $url, ?User_Feed $user_feed = null ) {
 		$mf = Mf2\fetch( $url );
 		if ( ! $mf ) {
 			// translators: %s is a URL.
diff --git a/feed-parsers/class-feed-parser-simplepie.php b/feed-parsers/class-feed-parser-simplepie.php
index 96d0326a..5e130ea1 100644
--- a/feed-parsers/class-feed-parser-simplepie.php
+++ b/feed-parsers/class-feed-parser-simplepie.php
@@ -232,7 +232,7 @@ public function discover_available_feeds( $content, $url ) {
 	 *
 	 * @return     array            An array of feed items.
 	 */
-	public function fetch_feed( $url, User_Feed $user_feed = null ) {
+	public function fetch_feed( $url, ?User_Feed $user_feed = null ) {
 		// Use SimplePie which is bundled with WordPress.
 		$feed = $this->get_simplepie();
 
@@ -381,7 +381,7 @@ public function no_comments_feed_available( $text, $post_id ) {
 	 *
 	 * @return     array  The comments.
 	 */
-	public function get_comments( $comments, $post_id, User $friend_user = null, User_Feed $user_feed = null ) {
+	public function get_comments( $comments, $post_id, ?User $friend_user = null, ?User_Feed $user_feed = null ) {
 		$comments_url = get_post_meta( $post_id, Feed::COMMENTS_FEED_META, true );
 		if ( ! $comments_url || ! $friend_user || ! $user_feed ) {
 			return $comments;
diff --git a/feed-parsers/class-feed-parser-v2.php b/feed-parsers/class-feed-parser-v2.php
index c46c9ee4..854b7e86 100644
--- a/feed-parsers/class-feed-parser-v2.php
+++ b/feed-parsers/class-feed-parser-v2.php
@@ -39,7 +39,7 @@ abstract class Feed_Parser_V2 extends Feed_Parser {
 	 *
 	 * @return     array            An array of feed items.
 	 */
-	public function fetch_feed( $url, User_Feed $user_feed = null ) {
+	public function fetch_feed( $url, ?User_Feed $user_feed = null ) {
 		return array();
 	}
 }
diff --git a/includes/class-admin.php b/includes/class-admin.php
index 1850a227..55b07f46 100644
--- a/includes/class-admin.php
+++ b/includes/class-admin.php
@@ -998,7 +998,7 @@ public function render_friends_list() {
 	 * @param  string   $catch_all The catch all behavior.
 	 * @param  \WP_Post $post       The post.
 	 */
-	public function render_preview_friend_rules( $rules, $catch_all, \WP_Post $post = null ) {
+	public function render_preview_friend_rules( $rules, $catch_all, ?\WP_Post $post = null ) {
 		$friend = $this->check_admin_edit_friend_rules();
 		$friend_posts = new \WP_Query();
 
diff --git a/includes/class-feed.php b/includes/class-feed.php
index df4de7e5..02f201e6 100644
--- a/includes/class-feed.php
+++ b/includes/class-feed.php
@@ -314,7 +314,7 @@ public function retrieve_friend_posts( $ignore_due_date = false ) {
 	 * @param      User      $friend_user  The friend user.
 	 * @return Feed_Item The modified feed item.
 	 */
-	public function apply_early_feed_rules( $item, User_Feed $feed = null, User $friend_user = null ) {
+	public function apply_early_feed_rules( $item, ?User_Feed $feed = null, ?User $friend_user = null ) {
 		$updated_item = $this->apply_feed_rules( $item, $feed, $friend_user );
 		if ( $updated_item->_feed_rule_delete ) {
 			return $updated_item;
@@ -330,7 +330,7 @@ public function apply_early_feed_rules( $item, User_Feed $feed = null, User $fri
 	 * @param  User      $friend_user The friend user.
 	 * @return Feed_Item The modified feed item.
 	 */
-	public function apply_feed_rules( $item, User_Feed $feed = null, User $friend_user = null ) {
+	public function apply_feed_rules( $item, ?User_Feed $feed = null, ?User $friend_user = null ) {
 		if ( is_null( $friend_user ) ) {
 			return $item;
 		}
diff --git a/includes/class-frontend.php b/includes/class-frontend.php
index b8edef20..2ea17458 100644
--- a/includes/class-frontend.php
+++ b/includes/class-frontend.php
@@ -963,7 +963,7 @@ public function header_widget_title( $title ) {
 	 * @param      array  $html_attributes    HTML attributes.
 	 * @param      User   $friend_user  The friend user.
 	 */
-	public function link( $url, $text, array $html_attributes = array(), User $friend_user = null ) {
+	public function link( $url, $text, array $html_attributes = array(), ?User $friend_user = null ) {
 		echo wp_kses(
 			self::get_link( $url, $text, $html_attributes, $friend_user ),
 			array(
@@ -996,7 +996,7 @@ public function link( $url, $text, array $html_attributes = array(), User $frien
 	 *
 	 * @return     string       The link.
 	 */
-	public static function get_link( $url, $text, array $html_attributes = array(), User $friend_user = null ) {
+	public static function get_link( $url, $text, array $html_attributes = array(), ?User $friend_user = null ) {
 		if ( is_null( $friend_user ) ) {
 			$friend_user = new User( get_the_author_meta( 'ID' ) );
 		}
diff --git a/includes/class-user-feed.php b/includes/class-user-feed.php
index f52dc6ac..e995dbde 100644
--- a/includes/class-user-feed.php
+++ b/includes/class-user-feed.php
@@ -44,7 +44,7 @@ class User_Feed {
 	 * @param \WP_Term  $term        The WordPress term of the feed taxonomy.
 	 * @param User|null $friend_user Optionally the associated User, if available.
 	 */
-	public function __construct( \WP_Term $term, User $friend_user = null ) {
+	public function __construct( \WP_Term $term, ?User $friend_user = null ) {
 		$this->term = $term;
 		$this->friend_user = $friend_user;
 	}
diff --git a/libs/Mf2/Parser.php b/libs/Mf2/Parser.php
index c09fefef..b8837a10 100644
--- a/libs/Mf2/Parser.php
+++ b/libs/Mf2/Parser.php
@@ -1386,7 +1386,7 @@ public function upgradeRelTagToCategory(DOMElement $el) {
 	 * @param DOMElement $context optionally specify an element from which to parse microformats
 	 * @return array An array containing all the microformats found in the current document
 	 */
-	public function parse($convertClassic = true, DOMElement $context = null) {
+	public function parse($convertClassic = true, ?DOMElement $context = null) {
 		$this->convertClassic = $convertClassic;
 		$mfs = $this->parse_recursive($context);
 
@@ -1420,7 +1420,7 @@ public function parse($convertClassic = true, DOMElement $context = null) {
 	 * @param int $depth: recursion depth
 	 * @return array
 	 */
-	public function parse_recursive(DOMElement $context = null, $depth = 0) {
+	public function parse_recursive(?DOMElement $context = null, $depth = 0) {
 		if ( $depth > 2 ) {
 			return array();
 		}
@@ -1529,7 +1529,7 @@ public function parseFromId($id, $convertClassic=true) {
 	 * @param DOMElement $context
 	 * @return DOMNodeList
 	 */
-	public function getRootMF(DOMElement $context = null) {
+	public function getRootMF(?DOMElement $context = null) {
 		// start with mf2 root class name xpath
 		$xpaths = array(
 			'(php:function("\\Friends\\Mf2\\classHasMf2RootClassname", normalize-space(@class)))'
diff --git a/tests/class-feed-parser-local-file.php b/tests/class-feed-parser-local-file.php
index ed1dd097..a1914e1d 100644
--- a/tests/class-feed-parser-local-file.php
+++ b/tests/class-feed-parser-local-file.php
@@ -25,7 +25,7 @@ class Feed_Parser_Local_File extends Feed_Parser_SimplePie {
 	public function __construct( Feed $friends_feed ) {
 	}
 
-	public function fetch_feed( $url, User_Feed $user_feed = null ) {
+	public function fetch_feed( $url, ?User_Feed $user_feed = null ) {
 		$file = new \SimplePie_File( $url );
 		$feed = new \SimplePie();
 		$feed->set_file( $file );
diff --git a/tests/test-feed.php b/tests/test-feed.php
index e989e2b9..d53bdf5e 100644
--- a/tests/test-feed.php
+++ b/tests/test-feed.php
@@ -137,7 +137,7 @@ public function get_rss2( $url ) {
 	 * @param      string $file  A SimplePie File.
 	 * @param      User   $user   The optional user, otherwise the friend_id will be used.
 	 */
-	private function feed_parsing_test( $file, User $user = null ) {
+	private function feed_parsing_test( $file, ?User $user = null ) {
 		if ( is_null( $user ) ) {
 			$user = new User( $this->friend_id );
 		}