Re: No greener grass
I really find that. But I've always been in the Gnome camp rather than the KDE one, at least since before any of it intersected with me starting to use macs. And I find Gnome very pretty these days, though I do make it like Ubuntu even when it's not. It is very possible my observation is more about the apparent responsiveness of the desktop environment, where straightline compute tasks ought, obviously, to be comparable. eg: a non-hardware-assisted handbrake encode ought to take the same time and if it didn't you'd wonder why (but of course if I have encoding to do I go back to macOS so it can use the media engine...) So it's completely in scope that KDE could give a very different experience.
But for me it started with a G4 Mac Mini, which I hadn't had very long before Apple stopped making macOS for PowerPC, so it spent most of its life running Linux, and very well. Long enough anyway to be completely slaughtered by a Raspberry Pi (2B I think), both running Mint. Which kind of woke me up to how old that poor G4 had got; why was I still spinning rust and fan to find a use for it when a not-even-current-then RPi completely outclasses it?
Various other macs in-between got the linux treatment, my feeling being that it's just what you do with an old mac Apple don't make operating systems for any more. Currently in that category is a 2019 Retina 5K iMac, now running Ubuntu doing light server duties. The desktop does run fine on it though, except that Linux can only drive it to 4K (and internal speakers don't work, and wifi and bluetooth...) but that's why, despite having bought several over the years, I kind of hate the iMac: display and computer have different lifecycles, and here's a lovely 5K screen being wasted, forever bound to an old computer that now can't drive it properly.