Might give more clues to others if you gave a bit more information. Did you use the distributions repository or the one from following the instructions to get the most up to date one from the Berkley site? (I did that and got the nightly build 8.1.0. When you purged boinc and boinc-client did you check that /var/lib/boinc-client was actually deleted? I know I had an occasion when I had to manually delete the files there.

jave@1950x:/var/lib$ sudo systemctl status boinc-client.service
● boinc-client.service - Berkeley Open Infrastructure Network Computing Client
     Loaded: loaded (/usr/lib/systemd/system/boinc-client.service; enabled; preset: enabled)
     Active: active (running) since Fri 2024-10-25 14:22:51 AEDT; 2min 53s ago
       Docs: man:boinc(1)
   Main PID: 1684 (boinc)
      Tasks: 2 (limit: 154290)
     Memory: 29.2M (peak: 33.0M)
        CPU: 923ms
     CGroup: /system.slice/boinc-client.service
             └─1684 /usr/bin/boinc

Oct 25 14:23:00 1950x boinc[1684]: Authorization required, but no authorization protocol specified
Oct 25 14:23:00 1950x boinc[1684]: Authorization required, but no authorization protocol specified
Oct 25 14:23:01 1950x boinc[1684]: Authorization required, but no authorization protocol specified
Oct 25 14:23:01 1950x boinc[1684]: Authorization required, but no authorization protocol specified
Oct 25 14:23:02 1950x boinc[1684]: Authorization required, but no authorization protocol specified
Oct 25 14:23:02 1950x boinc[1684]: Authorization required, but no authorization protocol specified
Oct 25 14:23:03 1950x boinc[1684]: Authorization required, but no authorization protocol specified
Oct 25 14:23:03 1950x boinc[1684]: Authorization required, but no authorization protocol specified
Oct 25 14:23:04 1950x boinc[1684]: Authorization required, but no authorization protocol specified
Oct 25 14:23:04 1950x boinc[1684]: Authorization required, but no authorization protocol specified

<cc_config>
<options>
<use_all_gpus>1</use_all_gpus>
</options>
</cc_config>

15-Jul-2021 19:15:23 Another instance of BOINC is running.

#!/bin/sh
boinccmd --quit

Best to use the BOINC Manager to directly add a project through the Add Projects function in the Tools menu than trying to add a project directly through the website.
Your problem is very common with a lot of projects invoking a ReCaptcha barrier and the solution to Join a project through the Manager is the easiest solution.

The other, more permanent, way of fixing this is to add the owner to the boinc security group:

sudo usermod -a -G boinc ownername

And reboot

A cautionary tale, never try to perform updates from memory when your memory is as bad as mine.

I’ve just spent an interesting hour or so recovering my system having entered the above command and missing out the -a.

So instead of appending Boinc to the list of groups my user was a member of it replaced that list with just Boinc. The sole user on the machine was therefore no longer admin and had no sudo permissions.

It turned out that the root user is disabled by default in Ubuntu so I had no way to correct the problem.

I tried booting into a live session from usb but the system is too clever for that, it still would not give me access to system files.

I eventually managed to get into recovery mode once I worked out that the grub access key has changed from space to esc since last I used it. From there I checked the sudoers file thinking to add myself to the list but that was identical to my working system. Then I looked into the groups file and that’s where the changes had been made. It turns out that they don’t hold a list of groups you are part of and append new entries, it works the other way round and the entry for each group has a list of all subsidiary groups so I had to add my user to half a dozen entries (guided by the groups file on the working system).

I now know a lot more about the inner workings of group permissions but I’ll never make that mistake again - until the next time my memory goes awol :-)