A very easy, and great method to watch YouTube on PS4 is to simply go to your PS4 browser, then type in the URL: www.youtube.com/tv
From there, you can pair your mobile device, or tablet to play the videos through the browser on your PS4 from Youtube. No flash required! To do this, go to “Sign in & Settings” then “Pair Device” and either scan the bar code, or enter the number from your portable device to initiate the pairing.
Quick and simple.