Personally, I dislike Zorin, but I can see your point. I didn't know it was Zorin at the time I I just find paywalling some FOSS stuff that isn't entirely yours very weird, and I also don't think users should touch almost anything Ubuntu-based, especially new ones. Mint might be the exception, but it's not to my tastes as well personally.
I think I agree with my university's Linux Users Group recommendation of Fedora, though I personally use Debian.
Honestly, if Debian would tidy up their website, make the Calamares-based installers the default, and perhaps had an installer with backports kernel built-in, it could be the easiest distro out there - I think everything else in Debian is almost perfect for most people. They don't even have to compromise on all that "universal operating system" stuff - they could just offer multiple installers. As for the website, I can get why they need to use a static site with HTML4, but that shouldn't stop them from designing a simple-to-use website.
Also, had no idea you were also in this community. Pleasant surprise.
I'm personally a fan of Debian. Default KDE isn't bad looking from what I can remember (I personally don't use it - I neither hate or love it just because I love XFCE). I'm personally a big XFCE fan, but you do have to do some work to get it working good, and there are still jank parts here and there.
While no distro is completely set and forget, I think Debian Stable is as close as you can get. Once you install it and get it working the way you want (depending on your setup, you might encounter minor issues as with any distro), it will pretty much stay that way until you upgrade to the next version, and you can go up to 5 years before upgrading.
I would recommend you use the KDE (or whatever DE you want) live installer, though, as the default installer is quite unintuitive. You can find it in the list of installers at https://www.debian.org/distrib/.
I've never used Kubuntu specifically, but I would personally avoid Ubuntu these days if just because of Snaps. Also, Ubuntu is heavily bloated - base Ubuntu is almost unusable in a VM now, while vanilla GNOME and PopOS run well in VMs on the same machine. Personally, when I need to test Ubuntu builds, I always prefer working with PopOS.
Overall, I'd say if you don't end up using Debian (I don't blame you - while I like it, you might not), just please don't use anything Ubuntu-based that isn't Mint or PopOS.