The person uploading may or may not be in the video, or the other participants could be under age. Figuring out the age of people in a video is lot harder.

Also stripe identity really works for US users the most , with a global audience like OnlyFans that could be limiting as well

Hmmm I guess you could use it and have snail mail as a backup...It'd be better than nothing probably?

Yea I'm not sure how you validate everyone in the video has a verified identity and age... Perhaps machine learning could automate some of this. Stripe has selfie validation... so if you could do something like that on the video where faces in the video are compared to the identities provided... If there isn't a match then the video is flagged for review.