Wanted to mention that Sailfish has a lot of closed-source components, especially UI-related, despite the overall marketing/"vibe" making it look very open. If anything, AOSP (Android) is more open than Sailfish. I don't think this has changed with Sailfish 5, see e.g.:
- https://forum.sailfishos.org/t/sailfish-os-clarifying-claims...
They are (slowly) releasing more and more components
https://forum.sailfishos.org/t/open-sourcing-proceeding/2468...
https://github.com/sailfishos/sailfish-weather/
https://github.com/sailfishos/jolla-camera
It's still more open than AOSP
If the openness is important to you, you may want to have a look at other GNU/Linux phones, Librem 5 and Pinephone. The former runs an FSF-endorsed Debian derivative.
Huh. I really don't see the point of this, vs something like GrapheneOS.
Edit: I'm well aware of the differences between typical Linux and Android (especially the security architecture!), and I'm willing to make some sacrifices in the name of FOSS... but only if it's actually FOSS.