Sorry, guess I wasn't explicit enough.
I was suggesting setting your Roku to your TV's actual resolution, not "auto detect".
I had the exact same issue on my Roku Ultra 2022 (4800RW). I tried all the fixes suggested by Roku several times. Even tried using 8K cables meeting the HDCP 2.3 standard. Nothing worked, UNTIL switching my Roku units. ROKU Ultra (4670) works just fine no matter what cables are used. This is to a Sony 65" XBR TV.
This started in early Dec 2022, may have been around the firmware update to 11.5. There were no HDCP issues prior to that timeframe.
The Roku Ultra 2022 (4800) is now connected to an LG 4K with no issues.
