The following code triggers Type '"listbox"' is not assignable to '"true" | "false"'lit-plugin(no-incompatible-type-binding)(2304).

<button aria-haspopup="listbox"></button>

That's not accurate. aria-haspopup can several values other than "true" or "false".

https://www.w3.org/TR/wai-aria/#aria-haspopup

I did a quick scan through the code and it looks like the bug may be in an upstream dependency. If someone can point me in the right direction I'll open a PR.