Call me silly, but I really like the movie seats and stage curtains overlay. It really adds to the experience, and I prefer to use it over stretching the aspect ratio or letter boxing. During the live streams, it definitely helps make it feel like an event.
I noticed that when you use the ‘cast’ button on the player, you lose the overlay on the device you are casting to.
if you cast through the browser options, it will preserve the overlay.
I have observed this on both MS Edge and Google Chrome.