It seems that there will be a release of The Cabinet of Dr. Caligari (1920) on UHD, 05/13/2022, in Germany. I don't know if it will be in HDR, but that's one I will probably be okay without HDR. I believe that makes this title the oldest on UHD and the first silent film on UHD. It's a good one, too! I'm not big into silent pictures, but some titles like this one are a must buy.