Manjaro KDE 20.1 (stable, testing and unstable), may affect other desktop environments also.
The issue is that if you logout and login then the login might hang
(or at least if you do logout/login two times shortly after another then the second login won’t start the desktop for sure only black screen and mouse is shown).
If the re-login works, the Plasma desktop symbols, menu and panel/taskbar often didn’t recognize fractional scaling settings (but all applications are scaled fine). Several new fresh installs of Manjaro KDE 20.1 with different branches didn’t solve the problem.
How do I proceed?