I find PentiKeyboard to strike a nice balance. You get six circles sized depending on where you put your fingers, and they contain most of what you expect from a regular keyboard, plus convenience chord for Ctrl+b to hasten tmux actions, in-keyboard cheat sheet and a character lookup and picker.

Ergonomically it's quite good, your fingers end up in a convenient place and when you want to reallocate your body you remove and reset the circles to new positions. The drawback is that on a phone you need to use both hands to type, but if you're doing something like programming or text editing you'll likely be rather involved anyway.

It's also nice that the keyboard doesn't hide half the screen, instead you can look through the circles or touch outside of them to temporarily hide the keyboard entirely.

Edit: Right, forgot to mention perhaps the best functionality, the sixth circle repeats the last bytes it sent, so if you do some action you have a button to just do it again and again. Comes in handy all the time.

https://play.google.com/store/apps/details?id=de.software_la...