Understood just to inform anyone that I downloaded the latest Rocky Linux 9.4 and Oracle Linux 9.4, Virtualmin fails and suffers from errors on the installation process failing some lines, but it still does trough, at least the installer does on Rocky Linux. No errors on Oracle, quite ironic 
Both do show repo errors after it’s installed, complaining about some packages related to python not being the best packages compatible. This happens after installation when you try to run an update. Initially, I thought it was just Oracle, but Rocky also has the same errors. I guess it must be something related to 9.4 which is very new and just released last month. I did the tests multiple (5 or more on each distro) with the same results, every time with a new scratch install.
As for the grade A supported distros, CentOS 7 is already EOL so that will probably removed from the list in the future. Which only leaves Rocky and Alma as supported grade A RHEL server compatible systems (free) since RHEL is obviously paid. But as I stated before, Alma Linux is actually moving away from being binary compatible or a RHEL variant like Rocky Linux, this means it will be even less compatible over Rocky, RHEL or Oracle in some future.
Guest tools for virtualization like Xen (which Cloudmin also uses) actually work fine in Oracle, but they don’t Rocky either, using same fedora RPM. So there is that as well. I will stick to Oracle Linux for now since I need them to run inside VM’s and hence they play better, probably because Oracle tests them in their own cloud which is also Xen (or was at least in the past).
Either way, as long as both Rocky, Oracle, Alma or any other distro remain binary compatible and are built from the Red Hat sources, it should really not matter, they should work more or less the same as they are same packages, same paths, same configs, but just with a different name or repo.
I would actually go with openSUSE if it was supported, I wish more software developers supported that distro since its quite nice and is also targeted as a server distro. Its now also 100% free even and direct build from their enterprise version, similar to what CentOS was to Red Hat.
Ubuntu, I consider this a more desktop OS, but it seems to be the popular server choice in Europe. I would not use Debian on servers unless they are VM’s because its very picky on hardware. Fedora, Stream, etc. I don’t want to be messing all the time with bugs and new versions. I actually want the longest supported distro if possible, in terms of security updates. Installation and setup, as well data migration, is a pain; hence I rather focus on the software inside, not the operating system. Red Hat/CentOS was the longest supported distro (except with CentOS 8 they screwed people) but now it actually seems OpenSUSE seems to be the longer supported distro in terms of years, I think I read it was 15 years, which is impressive.
Rocky Linux is nice, but I have a bad feeling about it. The reason is the same person that created it is the one that actually was behind selling CentOS to Red Hat, and it seems this is focused on a similar path, to partner or sell eventually. The reason I say this is that then the project was first announced, I and other people I know were involved, I mean from day one. The person behind, tried to pretend it would be all community based, even suggesting everyone to create a logo for example but actually, they already had the logo created and designed before they even posted that in their community. Why do I mention this? Because it was all marketing and fake.
They were never going to accept a design created by the community, they just tried to pretend they were so open that people could influence the project from day one. This gives me a bad feeling, similar to how some corporations like HashiCorp release open-source projects and change the license. You are either open source or not, my point it that I suspect Rocky Linux is in a similar boat which does not make that different from a corporate controlled OS like Red Hat, Oracle or OpenSUSE. Sure, it might not be a corporation, but it’s still entirely controller by a few persons they might sell tomorrow just like they did with CentOS in the past. They are getting more and more aligned to corporate distros as time goes by so that is also something to watch. Not saying it’s a bad thing, just that is something to consider.