Then I started reading about backing up databases, and it seems you can’t just back up the data directory (or file in the case of SQLite) and call it good. You need to dump them first and backup the dumps.

You can just back up the data directory, that works fine for selfhosted stuff generally because we don’t have tons of users writing to the database constantly.

If you back up /var/lib/docker/volumes, your docker-compose files for each service, and any other bind mount directories you use, then restoring is as easy as pulling all the data back to the new system and running docker compose up -d on each service.