Docker: updated from 18 to 22, upgrade won't finish. but data is now V22

Nextcloud informed me: V18 is no longer supported, so I set about upgrading it.

NC is running in a docker container. Looking on the internet I found what to do:

docker-compose down
docker-compose pull
docker-compose up -d

(Some of you may already scream at the screen…)

Everything looked good, but NC was now in maintenance mode, some more looking around:

docker exec -u www-data -it nextcloud-app /bin/bash
php /var/www/nextcloud/occ maintenance:mode --off

did not work, occ was in /html … same command with new location → worked.

Now I could click the upgrade button, but … then it said I cannot upgrade over multiple major versions …

So I tried the following in my yml-file:

image: nextcloud:19

Well now NC won’t start because: Data is version

What to do now?