HDMI 2.1 4K EDID Emulator (Model: 4K-EWB), Supports SCDC and EDID Copying and Emulation, HDCP Pass-Through (not Bypass), Pre-Set EDIDs are 4K@60Hz 4:4:4 and 4K@120Hz 4:2:0 with 2.1 Channel Audio

It’s a piece of hardware. Plug device into HDMI input on device then plug cord into it and ofc plug the other end into the other device. You power cycle everything after and when it settles, you hit the button on it so copies the handshake and it continues stays in sync regardless of power state of devices. The TV and Apple TV that I needed this on were years apart. Started after I upgraded to tvOS 26 Amazon one I ordered