Deactivate encryption

I have a nextcloud instance that was migrated from an old owncloud instance. In the security section it has these settings:
Enable server-side encryption - checked
Default encryption module - enabled
Encrypt the home storage - checked
The files in my data directory are encrypted indeed. What would be the procedure to deactivate the encryption? In the user data folders there are directories like encryption_migration_backup_2015-02-09_23-02-41
But I am afraid I don’t have any keys, not that I know of.

The instance works so far, I just want to get rid of the encryption. I have only a limited number of users, and the main content is all owned by me and shared with the users. So the other user content is not valuable.