The bigger players like Dell and Lenovo do and have for a very long time. Maybe HPE? Not sure

Then there are more bespoke vendors that cater specifically to Linux. System76 is probably the most well known, but there are many others.

I'm speaking mainly for laptops/desktops. For servers it's always been you just put whatever on.

Linux gets the most time on servers and containers but the desktop base continues to grow, so expect most problems to be there (bluetooth, wifi, etc.). Accessibility is getting much better.

It depends on your region and models.