No way that note8 cannot play youtube videos.
For me it works in the browser, as well with the standalone app. Be sure you have the Youtube app installed.
On the hand, adobe flash is not available officially, although you can get earlier legacy adobe flash that works more or less. For me it was very unstable.
Just google it.
Well, I don't use facebook at all, but like I said, unfortunately there is no official flash player available for Android, but I can give you this link