currently my biggest gripe with Linux on mobile is scaling. touchscreen gestures are broken in all wayland compositors, they divide the touch coordinates by the scale factor to process them and somewhere the fractional component gets lost.
if you've ever scrolled down a webpage side by side on a device running phosh and an Android device and thought "damn the Linux phone just feels worse" its because it can only scroll in 2 or 3 pixel increments.
fixing this would improve UX more than any other single change right now imo