Exactly. I have a full fledged emacs inside termux. With a Bluetooth keyboard, it is a surprisingly good solution. I bring this set up with me when I am on vacation and may have to do some emergency interventions for work. The only thing I have not figured out is how to re-bind the cap lock key for ctrl on the BT keyboard. BTW, I install emacs via Termux via their package utility. Termux itself is installed via F-Droid on my Android phone. One last thing: I also have tmux running inside Termux. Again, I am always surprised by how well this works.

I use my foldable bluetooth keyboard. Using iAWriter and termux, I can write posts for my PHP and ruby based blogs, run my static site generator and publish via git. Termux lets you make a shortcut that runs commands.

I tried to make gtk3 GUI apps with ruby on termux, apparently termux now supports this new mode that works in the browser, but some libs seem to be missing! I think that would be a cool platform.