Setup the “main host” as a regular domain with only “Apache” and “Apache SSL” enabled. Then under “Server Configuration > SSL Certificate” click “Set As Default Service Certificate”. Everytime the certificate is renewed, it’ll renew for Webmin/Usermin (Virtualmin) automatically.
Thanks @tnpsolutions,
I didn’t understand this bit-
‘Setup the “main host” as a regular domain with only “Apache” and “Apache SSL” enabled’
Does this mean
'Go to VirtualMin
select 'Create Virtual Server
Use the main hostname as the ‘Domain name’
unselect everything except ‘Setup Apache website’ and ‘Setup Apache SSL website’
It also will fail if server.domain.tld isn’t defined in authoritative DNS for domain.tld because it doesn’t yet exist anywhere, which is not an uncommon situation when setting up a new server.
In this case the DNS record was already set up and working, so maybe another issue. Not really concerned, just trying to be complete in case it helps others.