If you install BOINC 7.18.1 via the Linux Mint repository, or when you upgrade an existing BOINC-crunching Linux Mint 20.3, you are left with a non-working BOINC.
Via the Software Manager you can install the BOINC Manager version 7.20.2, which install itself in a hidden directory of the users HOME folder (in my case: /Home/Dirk/.var/app/edu.berkeley.BOINC)
That BOINC manager claims its data directory to be just /Home/<your username> in the boot up event log, but that is not my main irk.
- It does not recognize earlier BOINC installations,
- sees no installed virtual box,
- sees no Intel IGP (working perfectly in Mint 20.3),
- can't be contacted using BOINC Tasks.