HDCP with Mac Mini and an external monitor If I attempt to play movies on the TV app or Disney+ through the browser I am getting the following error:

This is with a newish LG 5K monitor connected to a 2018 MacMini via Thunderbolt.
Interestingly Disney+ works fine if I reboot into Windows via Bootcamp which tends to indicate the hardware is OK.
@jaume was correct, you want to use an HDMI cable if possible.
More information about High-bandwidth Digital Content Protection (HDCP)