| SYSTEM INFORMATION | |
|---|---|
| OS type and version | Debian 12/64bit |
| Virtualmin version | 8.0.1 GPL |
Creating the first subserver admin.mydomain.com worked just fine. Webmin/Virtualmin are now running smoothly in that domain after changing apache config and webmin config.
More subdomains cannot be created via the GUI - stuck after displaying “Creating Home directory” - while they can be created via CLI easily.
Did I misconfigure anything?
Yes, you have misconfigured something or caused it to be misconfigured.
The admin subdomain is reserved in Virtualmin. You should not / can not create a subserver for admin.domain.tld when a top level server for domain.tld exists in your Virtualmin system.
There’s a misunderstanding: I tried to create another subdomain cloud.domain.tld - which worked via CLI but got stuck via GUI.
@WardinT
this is imortant.
admin
you already created the sub-server admin before attempting to add another one called cloud.
probably the system should carry a warning to that effect. to prevent this and other “reserved” names 
So you are saying that this domain hierarchy cannot be created:
domain.tld
admin.domain.tld
cloud.domain.tld
another.domain.tld
And if so, why does it (at least seem to) work via CLI but not via GUI?
admin.domain.tld is definitely reserved.
but there may be others
cloud.domain.tld i do not think so.
but it is always a good idea to use some abstract name
as for CLI - i have no idea other than checks on CLI are often less applied because users tend not to use CLI