After some research on here and reddit about 6 months so, I settled on Borgbase and its been pretty good. I also manually save occasionally to proton drive but you’re right to give up on that as a solution!
The hardest part was choosing the backup method and properly setting up Borg or restic on my machine properly, especially with docker and databases. I have ended up with adding db backup images to each container with an important db, saving to a specific folder. Then that and all the files are backed up by restic to an attached external drive at well as borgbase. This happens at a specific time in the morning and found a restic action to stop all docker containers first, back them up, then spin them back up. I am find the guides that I used if it’s helpful to you.
I also checked my backups a few times and found a few small problems I had to fix. I got the message from order users several times that your backups are useless unless you regularly test them.
Reminds me of the group limit attribute in nextcloud. You could try looking at the ‘Custom profile scope’ section of https://docs.goauthentik.io/integrations/services/nextcloud/ to see if it helps to work out what to do