5K iMac as secondary display no longer allowing 5K resolution after Catalina

I recently upgraded my primary Mac to Catalina (my secondary mac was already on Catalina). Whether causal or coincidence, after my upgrade, I noticed my 5K iMac was no longer allowing me to use the highest available resolution.

Screenshot of secondary machine host OS showing that it is capable of 5K

Screenshot of secondary machine with Luna Display Secondary running showing that 5K is not offered

That means: when you in 10.14 macOS version, luna support 5k display?
Sorry about this question, because I didn’t test in 10.14 version, I’m in 10.15 catalina and have same problem with you.