Check out the YouTubers below for highly relevant writing and publishing advice.
Hello Future Me is a great channel for Science Fiction/Fantasy writers. There's a lot of focus on worldbuilding and magic, though there is emphasis on character development as well.
Bethany has a lot of great information for indie/self published authors. She has some character development videos as well, but she focuses a lot on how to put yourself through the publishing process.
Jenna Moreci is a character-development focused channel. She has a tons of videos on tropes and how to avoid them, and she also has a hilarious way of delivering her content.
Ellen Brock is an editor who specializes in characterization and plot development. She has great in depth videos on things like characterization over a series or writing the first page of your novel.
Alexa Donna is the perfect resource for authors who are looking to traditionally publish their books. She also offers craft advice on different aspects of your novel.