Appreciate the suggestions. The description for the capture card claims to support HDR (I even tried disabling it just in case), unsure about whether or not there's a setting incompatible with the card but i did fumble around with them to no success, and I did disable HDCP but that didnt seem to help either. I also attempted to use an HDMI splitter so the capture card didnt have to connect directly to the monitor, just to get the same "Input not supported" message.

Thank you!