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.