Dell iDRAC9 + Rocky Linux

What level of OS support is available for this device? Also, has anyone installed RL on a server with one of these? What was your experience?

Seems to work fine. Is there some specific functionality that you are looking for? As iDRAC is essentially it’s own OS/machine, not sure what you are worried about. The Dell repo seems to install and update just like CentOS 8 did.