Cannot run mysql after update to 20.04

Solution 1:

Inspecting the policy for the offending package I got:

$ apt policy mysql-common
mysql-common:
  Installato: 8.0.19-1ubuntu19.10
  Candidato:  8.0.19-1ubuntu19.10
  Tabella versione:
 *** 8.0.19-1ubuntu19.10 100
        100 /var/lib/dpkg/status
     5.8+1.0.5ubuntu2 500
        500 http://it.archive.ubuntu.com/ubuntu focal/main amd64 Packages
        500 http://it.archive.ubuntu.com/ubuntu focal/main i386 Packages

Hence I guessed something went wrong during upgrade to 20.04. I removed this package (along all the other related ones) with:

sudo apt remove mysql-common

Then the same command above returned:

$ apt policy mysql-common
mysql-common:
  Installato: (nessuno)
  Candidato:  5.8+1.0.5ubuntu2
  Tabella versione:
     8.0.19-1ubuntu19.10 -1
        100 /var/lib/dpkg/status
     5.8+1.0.5ubuntu2 500
        500 http://it.archive.ubuntu.com/ubuntu focal/main amd64 Packages
        500 http://it.archive.ubuntu.com/ubuntu focal/main i386 Packages

Installing again the removed packages (now from the focal sources, instead of the 19.04) with:

sudo apt install mysql-server ubuntu-desktop-minimal

fixed the issue.