How to convince a Windows user

My mate at work (20 yr old) )(I'm 70!!) cannot be convinced about Linux, just loves his W10 because it was free - and he's an IT Apprentice along with a being a big Steams user, and watching sports, Football, NFL and so on.

I need to convince him - this might help on the Steams front https://store.steampowered.com/
What else can I use to convince him?