To add to what @BrutalBirdie said, Cloudron is designed for hosting apps (and not databases as such). This means that you can't create databases separately and there is no UI to create/delete databases. It's designed for hosting your app which needs a database. The database is provisioned and updated as needed transparently as part of the app install/update/uninstall process. Very similar to heroku.

Just wanted to point that out, because Cloudron is not a classic style server management panel where one can manage "databases".

This is a feature; it was recently reported broken: https://forum.cloudron.io/post/24231 which was confirmed to be a bug: https://forum.cloudron.io/post/24232 due to be fixed soon

App names are whited out in this screenshot, but the display looks like this: https://forum.cloudron.io/post/23597 when it's working

got the same issue with one of my nextcloud's, even after removing the app, I could not restore the app to normal state, in the end, I noticed Circles app was throwing errors, disabled with

sudo -u www-data php occ app:list

sudo -u www-data php occ app:disable circles