[JeremyNT]

Not the OP, but I gave my daughter a Linux laptop as her computer running Arch Linux. I guess she got it at around age 7 (she's 10 now).

No issues with it. The (IMO, kind of sad) reality is that almost everything she needs to interact with is either web or cross-platform electron. The only real exception here is Zoom, which has a native linux client. She doesn't really need to understand much detail to use the machine.

She used GNOME before she ever saw Windows. We switched school systems and now she has a Windows laptop at school and her Linux laptop here, which she switches back and forth between without any trouble.

The only usability quirk is the LUKS FDE decryption phase, where she has to enter in her password before the system starts. There's no GUI and bad feedback on when she's typing, so it's confusing. But she understands what to do now and usually has no trouble (you might be surprised at how flexible kids are).