Trivial to who? A seasoned Linux nerd? Maybe. A regular, non-tech person? Nope. And that is why there is no year of the linux desktop. And if you expect a regular, non-tech person to be able to master the terminal and type in commands you're delusional.
Trivial in the sense of googling "how to install KDE on Ubuntu", picking a result that looks somewhat recent, and following those steps. It ends up being a handful terminal commands which shouldn't be too hard for anybody who has used a keyboard before. That's how I did it at least. There might be more UI centric options.
Also, trying to chase the elusive 'casual user' is what caused all the GNOME UX mess in the first place I guess. I'm not an 'archetypical' Linux nerd, I hate wasting time with fixing stuff that should "just work", but I'm also expecting a computer to be a professional tool which I can customize to my needs (within reason at least).
Windows is not better at this. Plenty of troubleshooting advice says "Now open the registry editor and..." or "Now open this .ini file and..." or "Now open cmd in admin mode and..."
The ease of the GUI ends when a serious system-level issue arises. This has never not been the case, it's just a matter of how much the documentation expects you to know what's going on, and how much that impacts the first-run experience. If the first-run is good enough, "reinstall" becomes the go-to fix.
I wouldn't expect a non-tech person to even understand the difference between an operating system and a desktop environment and why you can switch the latter while keeping the former. Nor would I expect them to care.
