Full linux system on phone, available as a desktop experience through hdmi out. Samsung phones have Dex, Pixel 8 has desktop mode in beta. In terms of general use, UI is pretty much there (Dex is ahead of Pixel 8 beta, but likely full desktop mode is coming). Code-server works pretty well for running visual studio code in a browser window. Portable external monitor with a keyboard or a lapdock is much nicer to carry, serves as an extra battery, and you get the advantage of having internet connection through the phone when there is no wifi.

But because of how termux is structured, compiling stuff isn't always straighforward. The team does a good job of building out the packages, but for example, stuff like pip install numpy should just work natively (in termux you have to install it as a system package). There is Proot, but its very slow.

I would pay for a better Termux that wraps all the necessary stuff so I can just do everything like I do under linux.