User friendly is pretty vague but if we're talking about the average user who uses the computer to browse the web, play some games on Steam with friends and do some document editing that is all covered. Linux Mint would be an excellent option. The installation is arguably easier than Windows (because you won't get all those pesky telemetry and data gathering questions), visually it looks and functions similarly to Windows, most standard software is handled by a package manager so no using terminal to install things and the distro prefers stability and ease of access over fancy bells and whistles.

If there are any user issues they're most likely because of third party developer not properly supporting Linux and there's nothing Linux can do. One example is anti-cheat for games. You can't play Riot games on Linux simply because their anti-cheat won't allow you to play their games on Linux and there's nothing Linux devs can do about it.

I don't know when was the last time you used Linux but I'd say the user experience has definitely improved in the last 10 years. It's gotten to a point where I'm actually willing to recommend Linux to users whose needs I'm familiar with and know they not going to have some weird needs that need the use of a terminal.

I also doubt the dev friendliness. GUIs are a godsend for software development.