Comment 4 for bug 1895157

I had the same problem in Ubuntu 20.10 and was able to get boinc working again by doing the following:

1. Stop boinc service and kill any boinc processes
2. Remove the gui_rpc_auth.cfg from /etc/boinc (It would probably be safer to change its name to gui_rpc_auth.cfg.old or something.)
3. Reboot computer.
4. Start boinc-client

After doing it, I found that the gui_rpc_auth.cfg was recreated with a password in it. This is a system generated password, not one that the user knows anything about.

I didn't have to change firewall settings.

Perhaps the reason that boinc didn't work in 20.10 was because a corrupted gui_rpc_auth.cfg file was included in the distribution. I noticed that the gui_rpc_auth.cfg file before I removed it in Step 2 above had a byte size of one byte. After is was recreated it was still a small file, but larger than one byte.

I probably had to temporarily change permissions in /etc/boinc, so this isn't a solution for a multi-user system, but hopefully it will give the package maintainers a clue on how to resolve this. Without a fix, boinc simply doesn't work in 20.10.