Found something: Apparently Recochoku occasionally sells music videos, but the store is blocked outside of Japan.

Yeah, things like interest of the right holders, contractual limitations and availability of a given media do play a part on getting published on a given platform.

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.

GOG tried, but either gave up or wasn’t able to keep supporting it (their communication is bad so hard to pinpoint). Now their movies section is just collecting dust, like Humble Trove was in the months before the old model was axed.