In short to see 4K video and the standards are set require for the communication between the devices HDMI 2.0 minimum or Display Port 1.4. However there is another standard that has to be met and that is due to the DCMA act and the special interests of the RIAA and the MPAA. For full 4K video, the security standard of HDCP 2.2 MUST be met. That means any device that is not compliant in the connected devices will invalidate the HDCP handshakes. Version 1.4 is not compliant with 2.2 and as such, if ANY HDCP 1.4 device is in the chain, the entire setup either will go dark, or downverts to 1080p. There are a lot of papers on this, but the following link explains this. I am very surprised that there is no sticky on this. I have battled this on the computer side and for AVR stuff the issues are the same. Many companies claim HDCP 2.2 compatible but don't know a flying (*&(*& about the actual standards. They cheap out using the old 1.4 standard and then bury it in the weeds or don't even disclose. Look for equipment if you want a minimum of 4K video that all devices you purchase make the claim of compliant and make it a priority to emphasize that. Don't be deceived, this is a real issue and cheaping on a component that does not meet the specification will cause issues. https://www.cnet.com/news/hdcp-2-2-what-you-need-to-know/
