Found this thread while looking for a solution to the same problem. Could this be a nextcloud issue and not a system/setup issue?
I get that the workaround is to run the update through the CLI but we shouldn't have to.
I'm receiving error "Docker Update Check not enabled" but as far as i can tell, the setting is enabled but i also have no dockers installed as this is a fresh install of unraid and i am slowly setting it up for the first time. I was wondering if someone can help me