If you're looking to build a bootable kiosk sort of thing, the old-school way was just a service file that ran xinit -- chromium --kiosk http://localhost/whatev

If you're looking to build a bootable kiosk sort of thing, the old-school way was just a service file that ran xinit -- chromium --kiosk http://localhost/whatever http://localhost/whatever. (no idea how to express that in wayland.) It's not locked down as much as you'd hope and there are a lot of details, but starting with that and letting the error messages guide your way is a workable approach...