Received error upon launching Docker NextCloud on my Unraid server.
Update needed
Please use the command line updater because updating via browser is disabled in your config.php.For help, see the documentation.

Restarting didn’t work, tried checking logs and tried via Console. Apparently this is a problem since the image was updated that disabled/removed manual updates on NextCloud on Docker.
Ran the following commands one after another from Unraid SSH session:
root@Tower:~# docker exec –user 99 Nextcloud php occ db:add-missing-indices
root@Tower:~# docker exec –user 99 Nextcloud php occ db:convert-filecache-bigint –no-interaction
First two command didn’t do anything and revceived exactly the same error. Came across the following command that solved it:
root@Tower:~# docker exec –user 99 Nextcloud php occ upgrade
During the upgrade obvisouly NextCloud gave me a maintenace page (progress!)

Note that the upgrae takes long and at some point it just sits there (and I run it on M2.SSD). You will see something similar in the SSH session, so just wait it out.
root@Tower:~# docker exec –user 99 Nextcloud php occ upgrade Nextcloud or one of the apps require upgrade – only a limited number of commands are available
You may use your browser or the occ upgrade command to do the upgrade
Setting log level to debug
Turned on maintenance mode
Updating database schema
Updated database
Update app calendar from App Store
Update app mail from App Store

Restore default tags that are missing

Starting …
0/0 [>—————————] 0%
Purify and migrate collected mail addresses

Starting …
0/0 [->————————–] 0%
Insert background jobs for all accounts

Starting …
0/0 [—>————————] 0%
Update app spreed from App Store
Restore default tags that are missing

Starting …
0/0 [—–>———————-] 0%
Purify and migrate collected mail addresses

Starting …
0/0 [——->——————–] 0%
Insert background jobs for all accounts

Starting …
0/0 [———>——————] 0%
Restore default tags that are missing

Starting …
0/0 [———–>—————-] 0%
Purify and migrate collected mail addresses

Starting …
0/0 [————->————–] 0%
Insert background jobs for all accounts

Starting …
0/0 [————–>————-] 0%
Starting code integrity check…

Finished code integrity check
Update successful
Turned off maintenance mode
Resetting log level
root@Tower:~#

Replace the user-id, docker container name with what you have and after that it should be good to go.