Sal is correct. Generally it all does. What I have had to do for my (old) Oppo is set the EDID for HDMI 1.4 compatiblity. Add to that I have a 2 K TV off the AVR, and a 4K monitor off the graphics card. Sometimes nothing makes sense and you just keep working with it until it does.I was assuming the HDMI would just work into my new AVR31 (when it arrives) but you're right to raise the spectre of it not. One more thing to worry about. I only have two HDMI sources at present, an Oppo 95 and a pair of Humax HDR Fox T2 digital terrestrial TV PVRs. These work fine into my 2014 era Sony TV. I also have a Roku 4 but I don't care if that doesn't work with HDMI since BBC iPlayer never worked on it anyway.
Nothing insurmountable, and HDMI is generally just fine.
I'm just "lucky". lol. If it can mess up, well, Murphy is always looking at me with his laws.