Comment by yndoendo
Don't know how the Google's actions with affect AOSP. There are few options depending on location / country with base band frequencies.
Murena with e/OS/ [0], Purism with PureOS [1], Volla with Volla OS or Ubuntu Touch [2], and Furei Labs with FuriOS [3].
Those are the companies actually trying to sell a phone versus Pin64 selling a device to tinker with.
Alternative is checking personally managed OSes like postmarketOS [4] and Ubuntu Touch [5].
[0] https://murena.com/ [1] https://puri.sm/ [2] https://volla.online/en/ [3] https://furilabs.com/ [4] https://postmarketos.org/ [5] https://www.ubuntu-touch.io/