I had a look where one would start basing a build on, there are at least two active repositories
- https://github.com/android-rpi/device_arpi_rpi4
- https://github.com/lineage-rpi (used by konstakang for Lineage builds at Raspberry Pi 4)
Both use the same (android12) 5.10-lts kernel currently. I guess the Automotive Android / AndroidTV builds are popular as people need to look for a screen by themselves.
Rpis have been discussed in this forum at