Technically Android still allows installation of anything if you use the debugging tool. Maybe that is where we have to draw the line, I'm not sure.
Are there consumer watchdogs in CA that would champion something like this?
Didn't Google recently kill AOSP and stop providing board support packages for their phones?
I've been wanting to get into OS dev for years now, I may make an attempt at it soon. When I was younger I built my own kernels for the early OnePlus phones. Maybe I can build an alternative to Android, doubtful but I like a challenge.
The hardest part to making an alternative is the app ecosystem, you almost need a complete suite of 3rd party apps built before you can get any initial adoption.
https://github.com/zenfyrdev/bootloader-unlock-wall-of-shame