There are some wiki pages about that, feel free to extend them if you're missing anything:
You can just open an apk file with this tool; apps don't need to be integrated with it. It's just that the implementation is far from complete and most apps will not work (correctly) right now.
"We have Lutris at home"
The mockup is discussed here:
https://gitlab.gnome.org/Teams/Design/os-mockups/-/merge_requests/17
