with Airplay Udemy video blackens the whole screen on TV but sound plays
Udemy Black Screen Video but Audio working - Apple Community
This seems to be old issue (above link), but the problem seems to persist. I have the same earlier several times reported problem with Macbook Pro mid 2015 and iPadpro 4th gen. All software updated, sidecar usage not even possible.
Now this problem appears not only on Safari, but Chrome and Firefox, too. Screen goes black if even a little of the video portion is visible on your iPad screen. If you scroll the page up so that udemy-video is off the screen, black screen on tv disappears and it shows rest of the udemy-page normally. Still I can play youtube videos with no problem, appears udemy-centric problem.
This has to be bug. Hope this gets fixed soon…
QAQ7D