TheShoe, that was the answer I was looking for.
All I want is to have the most direct signal directly from JRiver to my TV. IŽll set my display card to RGB 10 bits, so as you do.
Thanx a lot for your polite and helpful answer.
You're welcome.
One thing to look out for - and you will notice it if you see it while watching familiar video - is in scenes with what is supposed to be pure black (RGB: 0, YCbCR: 16, on a scale of 0-255 where in 0-bit color 0 == "black" and "255" == "white"), if you see a weird sparkling effect, like very mild static noise in the black part of the image, something isn't set correctly.
It's lost to time for me how I solved this as I've upgraded components over time and both the hardware and software (and HDMI cables, now that we have high-bandwidth needs) have improved so much. But I stand by my recommendation - RGB throughout the chain to my aging eyes produces the best results.
I don't think you'll see this effect - it's something "resolved" years ago. Just pointing it out. For me, my "test movie" was Labyrinth (4K UHD). In the opening credits when the CGI generated Owl is flying around, the background is and should be pure black. Back then (years ago), I saw the sparkles and it drove me crazy. Now I also noticed this in gaming as at the time I had one PC and it pulled double-duty: Home Theater (Media Center), and Gaming. In games like Horizon Zero Dawn, I saw same effect. In the end, IIRC, I set everything to RGB and it resolved. With older OLED then (the final 3D Capable 2016 LG curved display), as today, there are input settings for various modes: Movie, Game, etc.. which also have an effect as they enable/disable various settings. It's amazing rats nest of options and I spent countless hours trying to find the optimal.
At some point I was able to afford and build a separate gaming rig, put an HD Fury in-line, put video output directly to my OLED C1 for dynamic refresh rates, split the audio off to a proper processor (ARC over HDMI is just a poorly supported option) and dial in everything to where I need it. My only validation that it was time well spent is that both my children and my wife watch movies and listen to music (external DAC from Media Center) and they comment on how incredible the difference is! Validation. At a cost (time, money, time==money?). Now, I just leave well enough alone. JRVR is awesome - it solved for me at least my obsession for MadVR which went mostly private, and that's fine - that guy is genius. But so is Hendrik, and having him part of JRiver means we all benefit

Sorry - long winded post. Media Center beats *any* STB like implementation for Video (if anyone wants a Dune 4K Max Vision, lightly used, DM me), and destroys any STB for Audio by orders of magnitude.
Happy watching! (and listening)