Fairphones are pretty well supported with PostmarketOS which is mainline Linux. Audio support being one big feature that is missing on all of them. Luca Weiss from Fairphone is working on mainline Linux patches for these devices. The Fairphone 6 booted with Linux support on the first day it was released (though still missing many drivers)
https://wiki.postmarketos.org/wiki/Category:Fairphone
I wish Fairphone would hire more People to work on Linux support
This is dumb. Nobody is going to go back to dumbphones. Europe should fund projects like PostmarketOS which provide a fully free OS for mobile phones.
UbuntuTouch may be a bit more usable right now but it too depends on Android.
If Europe funded PostmarketOS and funded the development of a Linux-first mobile phone it would do itself a great favor.
I went all-in on proton a few years ago but I dislike the direction in which they are going now. Does anybody have tips on how (and where) to switch smoothly. I could self host email but I've heard that it's a big hassle
Difficult question. There's two types of Linux on Phones:
Ubuntu Touch is a downstream Project. They use the Android Kernel and HAL and put their own userspace on top. This is nice because you get many features working pretty easily. The problem with this approach is that you are sitting on top of an unsupported kernel which will not receive updates when the vendor stops supporting your device.
Then there's PostmarketOS which is an upstream Linux mobile distribution. There are many more devices supported but there are only a few which are working well enough to be daily-driveable. This is because you have to write new drivers for Linux. The Android kernel sources are available but porting the drivers over is hard. Many of them are in userspace too where we don't have access to them. The currently best supported device (IMO) is the Oneplus 6 or maybe the Pixel 3a. You can daily-drive those devices if you can get used to some quirks. (For example my touchscreen randomly stopped working sometimes on the Pixel 3a and I had to reboot. But this is fixed now)
https://wiki.postmarketos.org/wiki/OnePlus_6_(oneplus-enchilada) https://wiki.postmarketos.org/wiki/Google_Pixel_3a_(google-sargo)
I have tried using Ubuntu Touch for a while but I found it hard to tinker with because it uses technologies which are not used in the Linux Desktop stack, the rootfs is read-only which means installing packages is harder, and some more things which I forgot.
With PostmarketOS you bascially have a Linux Desktop machine in your Pocket with a mobile User-Interface which you can tinker with as you like. That's why I really like using it.