daankata
commented
2 years ago I fixed the issue by installing a third-party extension (Picture-in-Picture-for-Youtube, from pull request #66) and it works in application mode.
I am going to leave this issue opened, as for most users this isn't a viable solution because the extension is missing from the Web Store and has to be installed manually from Dev Mode. I also think that this is a basic functionality and should be in this extension, without the need to install a third-party one.
The extension is not working when Chrome is launched with --app mode from command line (or with PWAs). Expected behaviour would be to potentially show a mini PiP button when hovering a video (like in Firefox), or allowing to use the shortcut (Alt+P) inside the application mode.
*Extension (and shortcut) is working normally when not using application mode. Also, all other installed extensions inside application mode work fine.