There are phones that can run "true Linux" out there, and there even are ports of Sailfish OS for some of them, but Jolla phones were never part of those and rely on Android drivers instead.
Pinephone/pro
What else use main line kernel without blob ?
Seems that Jolla C2 can run "close-to" mainline kernel: https://forum.sailfishos.org/t/mainline-linux-kernel-for-the...