Oh lawd is there a lot. But that works for HHN specifically?
White Hornet. That’s where Slenderman originated from.
I Am Sophie could fit very well and have a tongue-in-cheek relatable plot (wannabe social media influencer is being haunted by an excellently designed demon that’s possessing and killing off her friends)
Salad Fingers would be great and was huge for a while
Daisy Brown is a series from the perspective of a vlogger who keeps around a bunch of gross mutated monsters as pets around her house
Dead Meat is also a really popular horror movie YouTuber that’s in with CryptTV and a few studios that I think could make a great original with an IP label house a-la Penn and Teller based on his Kill Count series
Just gonna throw FNAF on this list because it was essentially just a little known horror indie game until YT ate that thing up
There are also allllll of the classic Creepypasta tales and whatnot, but White Hornet (if marketed towards Slenderman) and Salad Fingers are the only ones that I can imagine having the same pulling power as CryptTV, though do that many people even know what CryptTV is?
But anyway this is hella off topic now but I just love YouTube horror