There are so many great players. Don't forget to include Steven Espaniola, Daniel Ho, Tavana, even Karlie G (even though she is known as a singer/uke player) I've heard some clips of her playing.
I recently found anathebandah: https://www.youtube.com/watch?v=uu920ftUwU0. She has a killer feel and a really original touch. Definitely the most exciting uke I've heard in a long time.
There are so many good uke people on YouTube, both players and reviewers, that I'm not going to pick a favorite. I go to YT occasionally and browse the ukulele sites.
Our own Brad Bordessa - for his deep insight into playing and performing (I always come away with a new concept to contemplate)
Craig Chee and Sarah Maisel - for all the great livestream lessons, concerts and festivals they host virtually
Ukulele Underground - Aldrine and gang for the joy and laughs
Cynthia Lin (with UkuLenny) - for the lessons and the Beatles jam livestreams
Hawaii Music Supply - Corey, Kalei, Mika, et.al. (the guys I most wish I could play like)
With in-person jams, festivals and concerts eliminated this past year, I've spent more time in front of YouTube to get my fill of ukulele lessons and inspiration.
I want to take a moment to give a shout out to this forum's Jim Hanks. I really enjoy his channel because of his sincerity. A lot of the elite gurus post videos that have obviously benefited from some post-production ameliorations. Jim's videos are raw with mistakes or, if not mistakes, then at least less than optimal moments. But he is living the life. He is stepping up to the plate, going for it, and getting it vastly right. I really enjoy watching a real person do his thing.
Ariel McCleary. I loved her channel when she was doing YT. Not only was she super funny and quirky, she could really sing! I really don't know why she didn't have more viewers than someone like Elise Ecklund (who I also watch from time to time).
Gotta throw in a thumbs-up for my friend Steve Rose, who just released his new ukulele album. He's also on YouTube and posts occasional tutorials and such. Here's one of his originals; it's got a lot more than ukulele going on so it's different than most: