Some (many?) HDMI cables can also carry Ethernet over HDMI. The main use seems to be to provide internet connection to a smart TV from a cable modem box. Currently I have an ethernet-USB adaptor ...
We have some video conferencing equipment at work from Neat - an all-in-one Zoom Room setup, that has an HDMI port for direct connection of a device. When the equipment detects a signal, it turns on ...