Minisforum V3 is 12” and less than 1kg.
But it is not quite a laptop, expensive and very powerful - not sure if that suits you.
Linux wise, most of the stuff works (volume buttons, fingerprint reader, face recognition, pen, touchscreen). Things that don’t work are automatic rotate/accelerometer.
Depends on their specific needs, so they should probably jump into some Linux community and ask for themselves.
My anecdotal evidence includes vastly different experiences.
I have a friend who hates Linux desktop and exclusively uses it for running commands via WSL.
Another who uses Linux desktop primarely, but dualboots Windows for certain games.
And I am on Linux single boot and use KVM sometimes for running my CNC or other software.