Nextcloud broken post-migration -- mysql/mariadb uninstalled?

What type of hardware are you using: Virtual machine
What YunoHost version are you running: 12.0.11
What app is this about: Nextcloud

Describe your issue

Upgrade failure!

I ran the migration last night, no issues. Unfortunately, on attempting to upgrade my Nextcloud install, I’ve run into problems.

The first attempt complained about not being able to find mysqldump:

https://paste.yunohost.org/raw/uvahalozuj

So I installed it (mariadb-client). The second attempt complained about not being able to connect to mysql.sock:

https://paste.yunohost.org/raw/izeyaxareg

So I went to check the status of mysql, and I get:

# systemctl status mariadb
○ mariadb.service
     Loaded: masked (Reason: Unit mariadb.service is masked.)
     Active: inactive (dead)
# systemctl restart mariadb
Failed to restart mariadb.service: Unit mariadb.service is masked.

So … how do I proceed? Why is mariadb masked? Can I unmask and restart the service? Nextcloud is kinda reliant on maria, and the Nextcloud instance itself is throwing an error when I visit it.

ETA: /etc/systemd/system/mariadb.service is a symlink to /dev/null … so that’s probably not ideal?

Share relevant logs or error messages

(See post text for log links)

A few more details …

  1. I checked my other Yuno, which is still running 11.x, and it doesn’t even have a mariadb.service in /etc/systemd/system, but the mysql services listed there link to /lib/systemd/system/mariadb.service, so I suppose that’s that.
  2. The upgraded Yuno system that this post is about doesn’t have a mariadb.service in /lib/systemd/system, which seems odd to me?
  3. My system, post-upgrade, has mariadb-common installed and has mariadb-client installed manually, as I noted above, but does not have mariadb-server installed. mariadb-server-10.3 and mariadb-server-10.5 are listed as “[residual-config]” in apt search – so it appears mariadb was stripped from the system during the migration and not reinstalled?

So … not sure what to do, here. Did Nextcloud change its back end somewhere between 29 and 30? (My other Yuno server is running NC29, which is still apparently using mariadb.) Is this an error in the upgrade? Third thing?

I can’t run a backup because there’s no DB. Config files are still there but not sure about data. I could run a force-upgrade, or uninstall/reinstall, or uninstall and try to restore from the scheduled backup a few days ago? Not sure what to do here. Anyone have any advice?

Opened Nextcloud won't start post-migration -- mariadb uninstalled? since the real issue was with the migration, not the upgrade.