As far as Existentialist philosophy(s) goes, there is quite a lot that an initial search on YouTube will turn up, but -- often the case with YouTube videos -- a good portion of the videos are lacking in certain respects. Some of it is a bit too short to really tell you much you probably didn't already know. Some of it is, quite frankly, rendered dull by the way it is shot or by the presence of the person speaking. Some of it is simply off-base, erroneous, tendentious. Still, there's also some good and even some excellent videos -- or video sequences -- to be found as well.
Existentialism saw its academic, and arguably also its cultural, heyday, back in the mid- to late-20th century That's when one might see public -- and video-recorded -- discussions by important players at the time devoted to the various philosophers or ideas gathered under its rubric. And so, we denizens of the present millennium get to enjoy -- brought back to new life by YouTubers -- such excellent explorations as Brian Magee's conversations with renowned philosophers, often bearing on other renowned philosophers.
One of those conversations takes William Barrett (the author of a long-classic work on Existentialism, Irrational Man: A Study in Existential Philosophy
It's well worth going on to the other portions of the show episode:
Perhaps the best part of the dialogue is towards the end, where Barrett contrasts Sartre against Heidegger, in many respects going against the grain of more popular existentialism-interpretation.