Well interestingly, one of the actual GTS manuals for '19 has the actual oil pressure reading indicated in the diagram instead of "OK". However in subsequent versions of the manual online, it just shows "OK" in that same diagram.
I talked with HD and was told that there will be a sensor kit coming out - but I havent seen nor heard anything more. I havent had the time to call HD and ask again, so if someone is inclined, let us all know
I am not concerned so much with what the oil pressure reading 'normally' indicates - ie: if it is 37, 31, 28, 25 psi or whatever at a given RPM, but I do care about any significant change from what it normally should be. Thats what I want to monitor. I added an oil pressure gauge to a TC88 and on hot days at idle at red light it would read just about zero, but I knew that was normal and didnt freak out about it. Bike now has 80K miles and going strong