There's always some post in here saying for people to use Linux. I find an admonishment to be pretty hollow, so I'll share my recent experience installing a Linux distribution rather than simply saying it's something people should do.
I installed one of the many Debian variants. Getting the installation media is certainly going to be a challenge for casual users. Otherwise, it was easy. It walked through the steps. It was different from installing windows, but I felt it was no more difficult. I am well versed in this stuff, but I feel like nothing in the installation process would be a problem for a casual computer user.
It offered several desktops programs at the login screen. This could likely throw off a lot of people. However, if you just logged in and ignored that you might never even know there were different options. The default was KDE. Everything worked. Nothing needed to be tweaked. This is in starck contrast to Windows, where once you get past installation, you need to get rid of a ton of crap it throws at you. The Windows 10 start menu is an unbelievable collection of weird boxes and shit and the task bar is similarly full of junk. The KDE start menu is just a menu. The task bar has your tasks. There's nothing to do.
I did try Cinnamon too. I prefer the simplicity. I don't think casual users are going to care.
Overall, I think for casual users, it's actually easier to set up and use than Windows. Getting installation media prepared is not something most people are going to readily do, but I think it's the same with Windows. They have the advantage there of having manufacturors install it. Otherwise, whatever issues there have been installing Linux distributions in the past aren't there now. Conversely, installing and especially the configuration after installation is much harder on Windows than it used to be. If you're slightly tech savvy, give Linux a try.