Having had some desktop difficulties, I write this in case it helps others with similar problems.
Leap 42.1 worked very well – I had no real problems. But as soon as I began using 42.2 (and later 42.3) several unwanted things started happening. My desktop PC system was running KDE with a GeForce 9400GT GPU which is Nvidia based.
Using Nouveau, desktop freezing occasionally, needing a hard reset.
Also with Nouveau, Firefox scroll bar and selection boxes invisible. Other apps (including browsers) appeared unaffected AFAIK.
With Nvidia drivers, after resuming from suspend mode, the text space under desktop icons is trashed (but the text is ok). Reboot required.
I tried a lot of things to fix it (including of course installing all updates) even a different GPU (MSI 710GT – also Nvidia based) but nothing worked.
Finally I decided to try a Radeon GPU and fitted a Sapphire HD6450 in a clean installation. The problems immediately vanished. I haven’t installed anything in the way of GPU drivers - whatever software comes with 42.3 KDE is clearly doing the job OK.