DS is 10 and has ADHD and is very impulsive (goes with the territory). He plays Minecraft and started watching YouTube videos of gamers and ditto Mario Kart but now goes off down rabbit holes of gamers who play games involving killing each other with cars/by pushing each other off cliffs.
He has a very combative relationship with DD and keeps using the same words to her and he's recently started a new SEMH school where he has a child in his class who calls him all kinds of horrible names, and he has also used the same types of phrases about this boy. School seem to allow YouTube as a relaxation/reward and he reports watching the same there ("so you can't stop me because school lets me").
He watches lots of harmless stuff and old TV programmes which aren't on YouTube Kids, and he doesn't do well with us telling him not to do something/that it's time to stop. We usually use timers or Family Link on the DCs' Android tablets to approve websites and apps.