Yeah, but you need the actual programs, and when I last looked termux didn't build packages that use X and didn't include the libraries to compile them yourself (or at least I couldn't find them)

GNURoot Debian might be a solution for you: https://play.google.com/store/apps/details?id=com.gnuroot.de...

It runs X, using the XServer XDSL app previously mentioned in this thread. I found some things rather quirky, but certainly fun to play with. My older Nexus 5 could do HDMI out with a dongle, add in BT keyboard and mouse, and it's mostly usable.

Doesn't run on Android 8.0 yet, and no HDMI out on my newer Pixel, so it's Termux + keyboard for on-the-go hacking.

Linux Deploy (also on Google Play) for those who have rooted their devices looks to be another choice.

You can use proot + debootstrap to install debian/ubuntu for example.

Some software could probably be compiled on a different ARM machine. Or would work when distributed in binary form. (Just speculation, but i dont see why not)