TBH I'm migrating manually by synching files. Still wonder if it's worth the hassle to somehow export/import contacts & calendar instead of reproducing them by hand. I thought about feeding the mariadb the psql dump I used to create for backups but that's probably more work than doing things by hand.

One reason for me to try docker is "easier" backup. I just throw the whole data-directory of the db container into restic. Restoring the backup would just be starting a container with that saved directory. I hope that way I don't have to argue with the database about reading a huge sql dump.

Unfortunately the documentation is a bit weird, I think. There's the official all-in-one container that starts a container that starts more containers but that was a bit too much "magic" for my taste. I used the images and documentation maintained by the community here and ended up with this compose file I can manage in portainer. Runs nextcloud (with apache), mariadb and redis. Also had to add that final bit for the cron job. This way I can point my reverse proxy at the local ip of the nextcloud_apache container and be done with it.