Android already is mobile: making it better makes sense. Linux already runs fine on it: termux and things like NOMone desktop combined with allowing virtual memory and keep apps running like some brands (Blackview, Oukitel) allow, you are there a lot of the way. Then Android desktop support (again, many brands have something already but it is now in Android mainline it seems). I use an oukitel rt7 as my main daily driver: it is rooted. It has some quirks and of course is very far from open, but things works, -ish. I would spend far more time on contributing if we had an open choice(or at least working) here that supports the 5g. On other phones/tablets, it is the fingerprint sensors, 3d face camera, but also different 'niche' auxillaries that would get far more attention if you at least can start with something that is (mostly open) and works. If we have coverage for a bunch of devices with everything working, it will be more attractive to work on other/newer ones.

With Linux, you will need, as I have seen on my pine phone, way too much focus on just basic apps which still are not good compared to their android equivalent: spending time there is not spending time on hardware support...