@KonstantinosGaitanis: I wish... I can't count the number of times I turned and flipped my device going through a dozen fake 'callibrate accelerometer' apps. Still getting into 'portrait' requires to set it completely vertically, and the 'bubble level' app shows it thinks it's flat, when it's roughly 45 degrees from flat. Tilt minimally sideways, goes into 'portrait' Set it on a flat surface and the screen flips upside-down.

This will cover my current situation. But I have another phone with older Android (and not enough room for upgrade), and I'd most welcome a solution for it too.

Could you link the app? There are dozens of Terminal Emulators, and most don't provide that.