I’ve been using Linux for so long that it’s hard for me to give an approximation of what a new user might find challenging
The average person would fail on step 0 of Installing the OS. In fact 90% of the problem could be attributed to Linux distros not coming preinstalled on PCs sitting in big box stores.
All of Linux's success stories for the average user (Android, Steam Deck, Chrome book) have one thing in common. They are low cost, simple, purpose built for very specific tasks with a bunch of exclusive games/software that people want to use. We need to start looking at PCs almost like they are highly moddable game consoles. It should come with the expectation that most users don't want to leave the comfort of the walled garden.