On my Ubuntu18 machine, I have installed python3.8 (i already had python2.7 and python3.6) globally and it corrupted Ubuntu UI. Most applications like chrome, LibreOffice dont open. The 'show applications' icon doesn't work. Top right tray showing volume, internet etc status has disappeared. Login screen is blank to start with. I could login anyway (hit enter and enter password - my account is 1st in the list). Terminal works and I reinstalled Ubuntu Desktop, unity, gdm.
I uninstalled python3.8 too. After hours, I upgraded to Ubuntu20.04.1 LTS (focal) and still no luck. Now I have only python2.7 and python3.8.
Any suggestions please? Anything i can do in CCSM? I see a ton of them and I think I have tried most, of course, haven't tried the right one.