Other than GOG’s withering “movies” section, I only remember of two that aren’t overly niche, DLsite and Fakku (both mainly porn stores). Maybe Itunes’ videos are DRM free, but I haven’t tested and still it would break the “no app” condition since it’s required for payment and download. Also maybe Itchio and Gumroad have something on videos too, since they don’t limit the types of media allowed there, but I have yet to confirm.