Sailfish is probably the most complete alternative to the big two. It’s got the biggest app ecosystem, first party hardware (meaning you can actually buy a device with it preinstalled - and yes Ubuntu Touch has a hardware partnership, too) and is based in Finnland.
https://sailfishos.org/
Not Android, not an Android fork, not reliant on hardware from the company you want to get away from (GrapheneOS requires Google Pixel devices).
Sailfish is probably the most complete alternative to the big two. It’s got the biggest app ecosystem, first party hardware (meaning you can actually buy a device with it preinstalled - and yes Ubuntu Touch has a hardware partnership, too) and is based in Finnland.
Unfortunately it’s not completely open source