Some video players can directly play video if you feed them a youtube.com URL. I personally use MPV, but if you're scared of the command line, SMPlayer gives you a nice graphical program that can natively play YouTube videos (as well as videos from a bunch of other video sites).
VLC works on phones, but not on desktop.
4/5
These are some very good suggestions and although I am a #KDE user, I am going to take a look (sometimes in a new light) at your suggestions.
One suggestion I would like to add, similar to Aberole is good old #SMPlayer (https://www.smplayer.info)
For years the number one recommendation for media playing on Linux was VLC, which almost always comes with distros. I always seemed to have issues with it and didn't like it very much. Came across SMPlayer and I think it runs rings around VLC in every way!
Again, thanks for your list!