The server is one of these URLs:
In pacman.conf you need to add the server like
# ArkSys Online server
[arksys-repo]
SigLevel = Optional TrustAll
Server = https://arksys-os.github.io/$repo/$arch
Note: $repo is the word between brackets [arksys-repo] and must be the same as name of the database 'arksys-repo.db' $arch is the architecture (x86_64, arm, ...) + the package name