You can still go to the host ip and log in, but nobody will be able to find any websites on that domain because the domain literally no longer exists. Only those that know the exact IP of the host server would ever find it.
What’s more, on a Virtualmin setup, it would have to be the default domain in order to see the website at all.
Correction: the expired domain will not resolve and must be accessed by its IP address, however if there are other domains hosted that are NOT expired, they should work assuming they have a path via DNS.
*** I believe this is what @Gomez_Adams intended ***