How is it gatekeeping? It’s is a trap though, there is literally nothing in those distros making gaming better. It’s like those “gaming” branded mice or keyboard that just have more color and a higher price tag. It’s there to attract people, but in the end you’ll get roughly the same performance whether you use mint, ubuntu or arch.
They don’t make gaming better, they make it easier for people who want to switch to have a functioning system, and there’s no price tag at all. Some will learn from there, some will just keep taking the easy way and that’s fine too.
It’s gatekeeping because without them only people willing and able to get technical get access to Linux. Would it be better if everybody learned? Of course. It’s not going to happen though, let others have a way in.
