What to do if I can't upgrade MariaDB?

Hi! I had to reinstall my personal NextCloud instance, and in the process upgraded from 20.0.4.0 to 21.0.3.1. Not too much trouble, luckily I had my old config.php. Now I’m greeted with the message

MariaDB version “5.5.57-MariaDB” is used. Nextcloud 21 will no longer support this version and requires MariaDB 10.2 or higher.

You’ve seen this a thousand times before.

Thing is, the database is running on my NAS and it looks like the manufacturer supplies an older version. That’s not great, but there’s not much I can do about it.

Now what? Do I leave it and hope for the best? Do I downgrade Nextcloud to version 20.0.5? Is that even possible? Have I messed up my database beyond repair?

Well, you should check your logs for errors and maybe you can host your database elsewhere on some dedicated VPS.

I think downgrade is not possible unless you have a backup…

Some NAS also let you generate virtual machines on their system, so you could run a newer version there. In theory, you could use a Raspberry Pi to run your database within your network.
For old routers, I have found alternative firmware in the past before I went for a fully open one, perhaps there are similar options for NAS as well.