Strange; I would have assumed that `dnf system-upgrade` would have made it from Fedora to RHEL by now.
Actually searching turns up https://access.redhat.com/documentation/en-us/red_hat_enterp... , which... appears to use a totally different tool? I don't really know what's going on there, but it does looks like they have some sort of support for in-place upgrades now.
Its was treated as "avoid of possible", but it loojs like that changed:
> An in-place upgrade is the recommended and supported way to upgrade your system to the next major version of RHEL.
As for RHEL-clones, your only choice is to use ELEvate(1), by almalinux, which supports other distros too.
But overall the process isn't as simple as Debian/Ubuntu, and on clones other than alma, you need to resort to third party tools, with some clones like Rocky saying that in-place upgrades should be avoided.
Actually searching turns up https://access.redhat.com/documentation/en-us/red_hat_enterp... , which... appears to use a totally different tool? I don't really know what's going on there, but it does looks like they have some sort of support for in-place upgrades now.