I have a 2013 MacBook Air and a 2015 Retina iMac, both running El Capitan 10.11.6. I don't want to install or enable Flash (for security reasons and on the laptop for battery reasons), but can't get most YouTube videos to play on Safari 10.0.2. I can view them on Chrome but would like to stay in Safari. Searched the forum but didn't turn up answers. Advice? Thanks.