Samsung discontinued support for Linux-on-DeX (which was always experimental/beta anyway). I assume whatever hacks they had in place to make the thing work were

Samsung discontinued support for Linux-on-DeX (which was always experimental/beta anyway). I assume whatever hacks they had in place to make the thing work were too hard to port to Android 10 for what was essentially a feature for hobbyists. You can still use DeX itself to get a desktop environment when you plug your phone into a dock, but it's an Android desktop environment, with Android apps running in floating windows.