I have a steamlink (physical) that I use in my bedroom to watch YT videos on my TV.
You can compare it to something like a chromecast/remote desktop, it basically streams the screen to the steamlink and allows you to control the PC with a mouse and keyboard from it.
When I put the video in fullscreen mode the video will freeze the moment the mouse cursor/YT UI is hidden (this does not happen on chrome) while the audio keeps playing.
When I move the mouse showing the YT interface the video starts playing again and stops when the cursor and mouse hides after not moving the mouse.
The video on the PC itself still plays fine.