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)
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.
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)