tiktok is entertaining, twitter is fine when it isn't full of drama, same goes for reddit, and I stay well away of facebook. Most social media try to keep you on their platform, so promoting video links to youtube, via other social media probably won't get you that much traction.
that said, sometimes twitter is good, and pinterest is surprisingly linked to YouTube. Out of all of them, I'd say Pinterest might be your best bet as it's all about sharing links, and next would be Twitter seems Twitter is fine with linking out to articles and such, so I would guess linking out to YouTube would also be fine in their eyes. Facebook restricts a lot of it.