I found a great app for iOS: PiPifier. It is a Safari extension that lets you use every HTML5 video in Picture in Picture mode — even Youtube’s which normally doesn’t allow that. PiP means that you can listen to/watching Youtube music in the background. It will continue playing if you leave Safari or Youtube App. Normally background playing is a paid feature (part of Youtube Music). I listen to youtube while driving, so background playing helps a lot.
Being in America 