MacBook – Difficulties with playing YouTube videos in Big Sur beta in Safari

Forcing Safari to quit works reliably for me. Double click the home button,tap the 'X' on Safari.

Try a reset: Simultaneously hold down the Home and On buttons until the iPad shuts down. Ignore the off slider if it appears. Once shut down is complete, if it doesn't restart on it own, turn the iPad back on using the On button. In some cases it also helps to double click the Home button and close all apps from the tray before doing the reset. It's worked for me