Linux

Mmh. Sure, I don't have kids so I probably lack some experience in how it is today.

I'm not sure if trying to compete with the attention-grabbing games is what whe should aim for. Sure kids love Roblox and Minecraft, and watching lets-play videos for days on end...

But there is no educational aspect in just giving them all the games. And they won't become invested in the underlying concepts and the world of free software and computers if all you do is replicate a gaming pc and provide them with a flawless Steam/Proton experience. The computer as a tool and the operating system is irrelevant for just gaming. And it isn't (in my eyes) what makes computers and Linux appealing.

I wouldn't even attempt to compete with that. Sure, give them SuperTuxKart, PPracer and maybe a Minetest world (with mods and animals and NPCs so the world isn't just the empty and boring default one).

I don't really know how to pry a modern child out of games and videos. Maybe restrict their time with that. Show them alternatives and how to use the computer as a tool. Start a project together with them. Maybe design a calender as a gift for someone, or get them started with the stop-motion movie, or music studio. You could also (dis)assemble the PC together with them and install Linux so they learn about the components. Unfortunately this all really requires time, attention and dedication from the adult and I see no way around that. And the child also needs to become interested in that aspect. But you need to start somewhere. I would really try to advertise this as something more than an alternative gaming platform and make some sort of distinction between the two.

[I know how it was back them with old computers and without the internet. We had a super old, decommissioned PC from my dad. The choice of games was somewhat limited and we had to become innovative. I learned programming relatively early, because Commander Keen or the old flight simulator wasn't as enticing as the modern games are and you got bored after a few days. With some games we got stuck or some were pirated and in English, which i didn't speak back then. So I definitely did a good amount of gaming, even back then. But we weren't allowed to do it indefinitely and we also sat in front of the PC with friends and took turns. I suppose this is different now that everyone has their own Nintendo Switch. The world has changed since and trying to go back isn't the right thing to do. But I believe the underlying concepts, trying to do more than just gaming and passive entertainment, restricting their access to it and provide them with alternatives, if you got the time to spare, is a good thing.]

(Apart from that, I've been with the boy scouts for quite some time. We always did some projects in the rainy autumn and winter. Even the roblox-kids from today like to do other things like hands-on projects, handicraft work to carpentry. But you have to find a way to reach them. Once they managed to get some nice results, it becomes easier and they become invested themselves.)