TikTok has longer content, some of it quite academic, but it's all vertical. I don't know about any one else's TikTok, but mine has a dedicated STEM feed if I scroll all the way to the left at the top. The problem is their vaunted algorithm will prioritize whatever content you happen to come across and then linger on, which tends to end up not prioritizing eg math content until you reset your algorithm and search for content you want the fresh algorithm to prioritize.