What are the main challenges in Linux adoption for New users, and how can it be addressed?

Linux does have better codecs and drivers than Windows for some stuff (Bluetooth for example), but it has worse codecs and drivers for some important proprietary hardware stuff (Nvidia for example)

Self updating without user interaction per default.

I think that this is a terrible idea, until a clear boundary is set between applications that can or cannot break the system. Updating flatpaks automatically might be fine, but updating everything is simply a recipe for disaster.