When I'm using my MacBook Pro 13"(M1 chip, Big Sur) and my iPad Pro as sidecar screen, some players (for instance the Udemy website player) in any browser I have installed turn black while playing, although the audio works fine and all the controls are working fine. As soon as I disconnect from sidecar I can play the video with no issues. I've tried to google this issue, but no luck. Any idea?
It's because of some video security measures that some streaming sites have. I've had this happen with almost all of them, including Udemy, Netflix and Disney Plus.
From Udemy's customer support:
Due to enhanced security measures on our platform, Udemy does not officially support video playback on externally connected monitors. That being said, we have found that video playback should function when plugging in a connector cord such as an HDMI cable directly from the monitor to your device (IE without the use of ports or docking stations).