This is neat: the Firefox 130 nightly build has an option to auto-open videos in picture-in-picture mode when you switch away from the tab they're playing in - handy! 
#firefox
OMG! Ubuntu
Firefox Nightly Makes Picture-in-Picture Mode MUCH Easier to Use - OMG! Ubuntu
The latest Firefox Nightly build provides a feature that dramatically improves how its picture-in-picture (PIP) feature works — and I'm tota...