If the only need you need is sync repos without exclusions or transformations I wouldn't bother, it could work for you until it doesn't when they archive it or kill it like kaniko or so many other google products/tools.
Gitlab has really simple way to mirror from Gitlab to Github or other git vendors/servers
Not sure why a full desktop required, perhaps a Raspberry pi 5 16gb,
the pi 500+ or any other mini pc or a cheap chromebook would be enough to start, obviously depends on the kid's interests
Gitlab has really simple way to mirror from Gitlab to Github or other git vendors/servers