Best lightweight OS option for repurposing older hardware?

My niece is turning 12 and we think she is ready for her own computer for school and personal projects. They have an older Thinkpad that works great from a hardware perspective, but it’s quite old and not capable of running modern software. I remember from long ago that there was a project called TinyXP that stripped a ton of stuff out of Windows and made it much more performant on low spec computers. Does anything like that exist for Windows 10 or 11?

I would prefer to stay within Windows for her and her parent’s convenience and so I don’t have to be personal tech support, but I am comfortable with Linux if there is something that fits the bill and would be mostly or entirely hands-off once installed.

I want to make sure she has a good experience, so if we need to buy something new (Chromebook, probably?) that is also an option, but of course saving money is also nice!

#tech