People here are saying that Waydroid works quite well for running Android apps on mobile Linux.

I tried postmarketOS a few months ago on my SHIFT6mq and for me, the dealbreaker was that I couldn’t get my SIM card to connect, so no mobile internet and no calls. As I understand, this strongly varies between phone models, though.
Aside from that, I did like what I saw a lot. I used Plasma Mobile and that was a more competent UI than stock Android, because well, it is essentially just Plasma with some tweaks. Felt a lot more like the pocket computer I never knew I wanted.