I finished an Any% run over 1:45 and it got rejected for no proof of IGT but I didn't see a place where I was supposed to add that?

If you really don't want to submit a video but a game board still requires proof of IGT (Dread certainly isn't the only board like this), it's common practice to upload a photo of the game's IGT screen to a long-term and reputable image hosting site like imgur (Google Drive works too, but you might end up deleting the file later), and paste a link to that photo in the video field or the run description.