I installed NextCloud via Docker on my Unraid server. I mucked up the settings on installation (hit next before reconfiguring NextCloud to use MariaDB). No worries, I thought, I'll just delete the docker container and start again. I <3 Docker for making mistakes!

But no matter what I do, I can't seem to get a "fresh" install. I've tried different folders, deleting configs, and different ports. The best I've been able to achieve (when it works at all) is:

apps directory not found! Please put the Nextcloud apps folder in the Nextcloud folder or the folder above. You can also configure the location in the config.php file.

It seems that there are some lingering settings somewhere that I need to get rid of in order to start again. What's the right way to purge a docker container so I can do a fresh install?