We definitely ruled out an expired license (during hours and hours of support calls). On some builds we would have all RCT functions greyed out, but ConfigMgr would happily stay running, while other RCT builds would cause ConfigMgr to crash immediately when trying to perform a RCT function, or when trying to access it from the left-hand menu. On some other builds it would just work.
For example - RCT 5.6.2407 worked for us, but 5.6.2409 would cause ConfigMgr to crash.
For example - RCT 5.7.2412 worked for us, but 5.7.2410 would have all the options/functions greyed out (unless we tweaked the appsettings.json file to change “RunInConfigMgrConsoleProcess”: false). Once RCT was not running in the ConfigMgr Process, then we gained access back to options/functions.
It has been a wild ride for us since RCT 5.4 (where we opened and started this thread).
Since the current build of 5.8 is working for us again on Server OS, we have our fingers crossed that the next build will also continue to work (which has not been the case in the past or us (as noted in the above examples)).
Bezzoh, we feel your pain. Hopefully this gets sorted out in the near future.
Yeah, it is becoming more and more confusing as time goes on. I have now 1 server which miraculously is working, both RCT… and MIK. I then replicated with another one exactly how I got into that position, and that one… MIK still crashes the console. No clues. Ticket opened with HP 
After initially thinking all well after being advised to overwrite ‘serilog.dll’ in the console root with the same named file from the RCT installation directory, it turns out that whilst RCT and MIK then appeared functional, it prompted a further problem of the console crashing if trying to access ‘Device Groups’
Fusion logs indicate a .net issue:
Can you send us the Fusion logs and check the Event viewer for any crash details.
Hi Garth, send on the 02/02 at 17:28 - If you cant locate this email I can go through this again and provide new logs tomorrow?! Cheers.
Still cleaning out my Inbox from last week OOO. But I found them. I have ask team mate to review them. I will get back to you “shortly”.
I dont suppose there’s been any further progress on this for anyone has there?