

Tbh, unless you want to suffer A LOT, the best option is to get any Android phone, install Termux and on top install any Linux distro you like (if you want easy mode, pay for Andronix which helps with installation).
Then you just run your Linux distro in a container on Android and view its virtual screen using a VNC viewer app.
That way you get a fully-working Android phone that can run most Linux apps without breaking your main phone use case. The only thing you are really lacking is low-level access because it’s running in a root-less proot container. So no hardware acceleration or other fancy hardware stuff.
I get what you are saying, but unless you buy a specific linux phone with some semblance of professional support (e.g. Pinephone) this won’t really get better. The best time to buy a Linux phone was a bit over 10 years ago when Canonical still actually supported Ubuntu Touch. That was pretty much the last time there was any serious effort in that regard. Since then it’s just been hobbyists doing hobby things in hobby quality.