UNIX V7 didn't natively support the RL disks and RK's are too small, but someone did conjur something up for V7M on an RL02 (see the archive_details.html link, below)
https://minnie.tuhs.org/PUPS/node6.htmlThere are indications that 2.9BSD should run on an RK or RL, and 2.11 BSD should run on an MSCP disk.
I would expect that there are system images for RSTS and RSX floating around somewhere. At worst, I'd expect one could build such images under SimH and then transfer them to the Unibone/Qbone.
JRJ