Over all I think Virtualmin is doing well on CentOS 8. But easy for me to say since I usually start from scratch, not to mention I’m not responsible for anyone’s email but my own. For a production situation definitely follow the migration advice you’re getting. My only advice is to consider your comfort zone before upgrading. CentOS 7 may be showing its age but I doubt you’ll see a lot of difference with CentOS 8 in quality of service. I read that Red Hat tried to make the transition from RHEL 7 to 8 less traumatic than 6 to 7 turned out.
Me and CentOS go way back but I’m new to Webmin/Virtualmin and I’m mostly trial running. My first CentOS 8 installation had a lot of problems. For my second attempt the following post was very informative, particularly in regard to suexec, and especially how to avert a few common problems.
With CentOS 8 you’re likely to run into obstacles that evolve into delays that wouldn’t occur on a refined distro like CentOS 7. For example, because of some Red Hat bureaucracy, installing something as innocuous as whois on CentOS 8 involved extra time and effort when normally it comes straight from the EPEL repo using ‘yum install whois’. Here’s the lowdown on that:
https://forums.centos.org/viewtopic.php?f=54&p=313836
Webmin offers a way to install packages but I installed whois this way (install both packages):
dnf install https://archive.fedoraproject.org/pub/archive/epel/8.1/Everything/x86_64/Packages/w/whois-nls-5.5.1-1.el8.noarch.rpm
dnf install https://archive.fedoraproject.org/pub/archive/epel/8.1/Everything/x86_64/Packages/w/whois-5.5.1-1.el8.x86_64.rpm
I’m seeing other unusual issues with package installations that I’m still learning about. For instance, with CentOS 8 I’m noticing more source src.rpm packages in addition to binary rpm packages, and certain source packages don’t seem to build correctly or are incomplete in some way. One example I experienced is the Redis 5 package from the AppSream repo, which ultimately worked out but only because of manual intervention that was never necessary on CentOS 7.
There were other installation headaches that I’ll probably bring up in separate posts. So far everything came out in the wash and Webmin/Virtualmin seems happy on CentOS 8.
Hope this offers some perspective.