CLI command qm is your friend. List/manipulate VMs and such with this utility.

The automatic package update script will fail, because ProxMox “assumes” you will have a subscription (silly ProxMox). To fix this, the process must run at least once (and fail) and then it can be flipped to the “no-subscription repository” as follows…

Select “Repositories” underneath “Updates”
Disable the ceph-quincy and pve repositories
Click “Add”
In the Repository drop-down box, select “No-Subscription” and click Add.