There is a whole channel of theatre on YouTube many have not even heard of. Lately, the art of parody theatre has become more popular, especially with the Off-Broadway production of Puffs!, a musical about Hufflepuffs from Harry Potter, since they do not get as much love as the other houses often.
Believe it or not, this is not the first Harry Potter parody to become popular. Team Starkid, a YouTube channel that has been around for years, started A Very Potter Musical 9 years ago, and since, there have been two more Harry Potter parodies, a version of Aladdin from Jafar's perspective, a Batman parody, a musical about cavemen, and a whole lot of other really cool concepts. Each musical is approximately 2 hours long, and with almost a decade of content, there is plenty to watch! As well, it is all original content, so you'll have a whole new set of show tunes to get obsessed with.
Here's the link to their channel: https://www.youtube.com/user/StarKidPotter/videos
As well, if you have not heard of Todrick Hall, you're in for a delight.
I've been obsessed with Todrick for a while now, mostly for his covers and parodies, from a 90s medley to a Beauty and the Beast with only Britney Spears songs. He has so much content that you'll be busy for a while, especially if you go into his full-length visual albums, Straight Outta Oz and Forbidden. The first is more of Hall's personal story with Wizard of Oz themed songs and a super pretty album with awesome costumes and even some special guests!
Forbidden is much more of a social commentary piece, and it flips social stereotypes between races and gender. For instance, a White boy is shot in a Black neighborhood for looking suspicious and gay couples are the norm for the town. I am not as big of a fan of this album, but it does have much less of a musical theatre vibe than Straight Outta Oz.
If nothing else, you can see Todrick's vlogs about being over in London in the West End production of Chicago. He is best friends with Taylor Swift, and it is adorable.
Additionally, there are so many full-length musical movies and full length bootlegged shows. I have watched many a thing at 2am when I am bored, and YouTube is fantastic for people getting creative with the titles of their videos.