There's one issue that is bothering me with Ubuntu on my tablet: why does the default on-screen keyboard not have any special function keys like Esc, Ctrl, Alt, Tab or arrow keys? That makes using e.g. terminal in tablet mode pretty much impossible.

In another question about that topic from 2019 I found an answer saying the default keyboard is generated from Unicode, which does not contain these special characters. That's fine, but if you want to actually use that keyboard actively with Linux these non-Unicode special keys are absolutely essential. I'm a bit puzzled by this.

Part one of my Question: is there any way to enable at least arrow keys, tab and ctrl in the default on screen keyboard?

Part two: in similar questions it was recommended to install onboard or florence as an alternative. If it's not possible to extend the default keyboard with special keys, how do I switch the default keyboard that comes up when I try to input text in a text field to another keyboard? I have onboard installed, but the default keyboard still comes up and besides launching onboard manually I couldn't find a way to make accessibility mode default to onboard.

Thanks a lot in advance!

EDIT: Ubuntu 21.04, using default on-screen keyboard.