[az09mugen]

May I add this link to your interesting list : https://volla.online/en/

[pabs3]

Volla OS looks like an Android fork, so more like GrapheneOS than postmarketOS/etc.

[az09mugen]

When buying the phone you can choose to have it with Ubuntu Touch instead of Volla OS. There is also multi-boot.

[seba_dos1]

Ubuntu Touch is still an Android-based OS (they used to have a variant that didn't rely on Android, but discontinued it).

[az09mugen]

Thanks for that precision, I didn't know about that fact. For those interested : https://wiki.ubuntu.com/Touch/ContainerArchitecture