I know I can use an HDMI source like a Raspberry Pi and a small screen for HDMI and could twist copper cable together and measure continuity through them to narrow down which is which but I’m wondering if there is an easier way. Maybe something I connect to either end?
Maybe not easier, but network cable testers can send a tone through allowing you to plug the sender at a wall jack and use a wand at the terminal end to see which plug is which. The wand picks up an audio tone through the cable.
You’d need one with alligator clips or something rather than just network connections though.
Alternatively a multimeter and just measure for resistance on the cable itself, like at the outer shielding? Never tried, but I think it would work.