Can you test. Perhaps it does work.
sudo -u www-data php /path/to/nextcloud/occ encryption:disable
Read
Invalid private key for encryption app. Please update your private key password in your personal settings to recover access to your encrypted files · Issue #8546 · nextcloud/server · GitHub
and test this at the end of the post
"Invalid private key for encryption app." I did not change my password - #2 by select