Bumping this thread as well.
I recently switched to Linux and I’m honestly surprised that there’s still no built-in solution for properly scaling the UI in Unity. On high-resolution displays the editor UI is extremely small, which makes it pretty uncomfortable to work with.
The workaround suggested by @CSEliot-KiteLionGames works quite well on my Fedora 43 KDE Workstation, so thanks for sharing that 
. In my case it actually makes the UI a bit too large, but it’s still much better than working with the tiny default scaling.
Hopefully Unity will add a proper built-in UI scaling option for Linux in the future.