You’re right. I was mixing up USB and HDMI specs. 2.1 is the Current HDMI spec. As for cables... https://www.hdmi.org/spec21Sub/UltraHighSpeedCable
For 4K and higher resolutions, Dolby ATMOS audio, eArc etc., you really want newer HS spec’d cables.
“For 4K and higher resolutions, Dolby ATMOS audio, eArc etc., you really want newer HS spec’d cables.”
1. These are the first ‘spec’d’ cables.
2. Notice that it says these cables are not required.
3. I am running 4k DHDR ATMOS fine on my old cables.