I found Samsung DeX to be usable, if a bit awkward at times. By far the most annoying limitation was being limited to Android and not being able to install more powerful software. Termux is stuck on a version in the Google play store because apps may not longer be published using some features Termux requires.
Years ago Microsoft did try the other way around - making Windows into a touch/mobile interface - but made both the desktop and mobile experiences a bit worse. Several linux-based projects are attempting to bridge the gap there, but they are often limited by compatible hardware and a lack of openness mobile device component manufacturers exhibit.
Google and Apple have very little economic incentive to open up their ecosystems. It really shows comparing how open Android used to be in comparison to how it is now.