@Gargron for now users can PiP in Chrome

A new way to PIP

Just head over to
chrome://flags/#global-media-controls-picture-in-picture

flip the flag to ‘enabled’, click that blue restart button and the next time you pull up a video that supports PIP (YouTube is the obvious choice, but many services use it), you can now look in your notifications tray for a new PIP button

works with Mastodon embedded vids