Signal is not currently possible (or at least practical). That's muly main blocker right now.
Linux Phones
The discussion on linux-based phones.
Linux Mobile Distros: Postmarket OS, Ubuntu Touch, Mobian, Sailfish, Manjaro Arm, Pure OS, Plasma Mobile, LuneOS.
Linux Mobile Hardware: Librem 5, PinePhone, Volla Phone.
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Okay that’s a dealbreaker for me to be honest. I basically used all the social capital I had to get all my friends and family to start using Signal, I can’t just stop using it ahha.
I assumed Signal and FOSS apps would run fine in an android container of something. Is that not the case?
You can run Signal on Waydroid yes, last I tried (about a year ago) the on screen keyboard didn't work right, and there were issues with Push notifications. Maybe things have improved since, but nonetheless it's a pretty crappy experience.
I would not suggest the pinephone as reviewers have stated it has slow performance.
You should check out the compatibility levels with the distros such as Postmarket OS, Ubuntu Touch and Mobian on their documentations before buying an used phone.