The title is "how to download brawl stars on PC" , and after a quick google search, brawl stars is a mobile app, meaning if you wanted to doanload it to PC, you'd have to use some sort of 3rd party method which would more than likely be against their terms of service.
The copyright aspect would not necessarily be on the footage of the game, but the instructions on how to download it to a platform they haven't licenced it's use onto. Much like how Niantic will ban users for installed Pokemon GO onto pc's running mobile emulators. In this situation, there's probably nothing you can do about it. It's evident they don't want people installing the game onto PC, and you showing people how to do that would be in breach of their copyright. I mean, legally you might have a leg to stand on, but I'm not a lawyer and none of this is legal advice, but if you want to fight it, to see if you have some grounds to fight on, you can probably contact a lawyer, or you can reach out to the game developers personally, but I don't like your chances.
I'd suggest just accepting that it is what it is, and you need to be careful when making videos about how to download games to platforms that aren't native to the developers wishes.