It depends on how much time you want to spend learning it and become a power user.

1. If the answer is ‘enough’, the best distros out there IMHO are Arch-based (Manjaro, EndevourOS, Arch itself). Plus the community is the best.
2. If you aim for a more ‘set and forget’ experience, I’d go for Ubuntu LTS as base with KDE. In particular, I’d go for Kubuntu LTS or KDE Neon.

If your reasonably tech-savvy and you are in for the long game, I suggest to go for n. 1: it’s a worthwhile investment.

Debian with Mate is perfect as far as I can tell.

If you choose to give Fedora a try, I recommend Ultramarine, which has more set up from the start, including their “Terrs” repository with more updated packages.

My top picks currently for distros that support KDE are the following:

• ArchLinux
• Debian
• Fedora KDE
• OpenSUSE Leap
• OpenSUSE Tumbleweed

For your use case (Nvidia, Wayland preferential), the better choices among these will likely be the rolling releases (OpenSUSE Tumbleweed, ArchLinux) or 6 month point releases (Fedora KDE). Debian and OpenSUSE Leap are solid choices for LTS, but given the state of Nvidia and Wayland, it’s best to use the latest releases of KDE and the proprietary Nvidia drivers. If you switch GPUs to AMD or Intel in the future, you should have no issues using any of the distros listed.

To put points against some of the distros your contending list:

Many of the direct Ubuntu-based distros tend to have a certain level of lesser quality in packages (such as many releases never end up pushing bugfix patches that get patched in many other distros including Debian). Additionally, there is no guarantee that Ubuntu-derivative distros that don’t directly source from Ubuntu software repos may have breakages when using PPA repos or developer-distributed .deb packages.

I’m sure you’re aware of this bit as well, but the mainline Canonical-maintained distros (Ubuntu, Xubuntu, Kubuntu, etc.) rely heavily on Snap: a containerized application platform similar to flatpak, but with no freedom of choice of package sourcing. Every Snap package will be pulled from Canonical’s proprietary publishing platform. A lot of derivative distros (Linux Mint, Pop! OS, etc.) end up stripping out Snap from default installations and removing package redirects, recommends for Snap.

For Arch derivatives (Endeavour, Manjaro, etc.), don’t expect to be able to use AUR packages without issues unless your derivative directly sources from the ArchLinux repos. Many AUR packages explicitly expect the latest packages, which some derivatives defer updates to, causing breakages.

In particular, Manjaro has a track record of poor maintenance and questionable choices (recommending users to roll back system clocks after forgetting to renew TLS certs, shipping outright broken versions of Asahi Linux in order to tout support for Apple hardware, DDOS’ing the AUR, etc.)

Debian Sid (the unstable (rolling) variant Debian) is an option, but it’s really not recommended for end-use, and mostly only for testing.

To put points against some of the distros on my recommendation list:

Fedora explicitly only ships with FOSS software. This does mean that initial NVidia driver setup is more involved compared to most distros. The process shortlist is initial boot with nomodeset, install rpmfusion repos, and then install the NVidia drivers from RPMFusion-nonfree. Once that is done, the proprietary drivers should be installed and all configurations necessary should already be made. Simply rebooting should allow using the system accordingly.

Installing ArchLinux specifically expects some knowledge of the inner workings of a Linux system. Modern Arch live images do come with Archinstall: a utility that assists in getting an installation from configuration options. In general, an Arch install is a more involved process. ArchLinux also expects that you read from the news page before pushing updates to your system. While this kind of practice can also be true for many other rolling systems/point releases between feature upgrades, it is fairly imperative that due diligence and backups are taken on Arch systems when updating.

I started the ubuntu path on warty, was a distro vagrant after unity arrived, switched to debian a while which was and is fine, decided to give manjaro a shot and couldn’t stand it, but oh how that AUR made me swoon. Finally worked up the nerve to lose the training wheels and try just arch, got tired of the immense chore that it became and found EndeavourOS.

I cannot recommend endeavour highly enough. It’s exactly what I always wanted and as long as they don’t completely shit the bed somehow I doubt I’ll ever leave. I can’t speak to your hardware concerns, as I went full team red with common hardware for my last few builds because I knew they would have linux on them. The arch wiki is great. The forum exists. They have a plasma version.

The only games I have been unable to play are those that have shitty anti cheat software and the occasional very recent release, but those usually get resolved in a hurry. Genuinely no complaints.

I’m going to risk the down votes. Stay away from atomic distros and you should be OK. Yes, they are less likely to break by messing around, but also infinitely harder to set exactly to your liking.

Since you are narrowing down on Tumbleweed, here are my 2¢: After more than 15 years of Kubuntu I installed Tumbleweed a few years (two?) ago, because it offers a rolling release, system snapshots and KDE.

Having a job and a family, I do not have the time to tinker anymore, so I expect things to work smoothly out-of-the-box nowadays.

Tumbleweed let me down in this respect.

Once I had to completely reinstall the system because the snapshots filled the system partition during an update, which made it unable to start KDE. I could roll back from the terminal to the previous snapshot, but couldn’t figure out how to remedy the problem, except for using a greater partition and reinstalling.

And just a few days ago KDE (and many applications, when used in LXDE) wouldn’t start, because of version mismatches (caused by an incomplete update?) that broke the linkage of qt libraries. To resolve it I had to make a decision between two packages (tlp vs tuned) to finish the update, even though I hadn’t installed those manually and didn’t know anything about them.

Besides those problems I find the administration suboptimal, with the divide between the Interfaces of Yast and the KDE settings. I didn’t manage to get my Brother network printer to work (except via direct USB connection), which worked out of the box with my android phone.

Get back with results. I switched from Pop!_OS to Fedora KDE today. So far my annoyances with Pop and Gnome are gone and what little I had time to try out with Steam worked well. The kernel is on par with pop. I’m used to Debian based distros and using apt from the command line so it will be a learning experience, but damn the Fedora GUI for packages is streets ahead I must say.

I really enjoy Tumbleweed. I’ve been using it for about 18 months now without issue. One thing to note though is that TW only packages production release Nvidia drivers. This means you will not have the 555 or 560 drivers that make Wayland usable by default. You can always install the latest drivers with the run file provided by Nvidia. Some people also use the CUDA repo to get the newer drivers. However, I’d think both of these options may be the type of tinkering you are trying to avoid.

Overall I think TW is a great distro but it may be a bit more setup for Nvidia gaming on Wayland than you are looking for. If you’re down with doing a little tinkering or gaming on X give it a shot. You can always roll back if something gets messed up.

Endeavour and Tumbleweed are my preferred choices here. They are rolling release and should be relatively stable.

I know you said you want to use KDE, but Pop is actually working on their own DE, called Cosmic, to be released with the 24.04 version. It’s currently still in alpha, so it’s far from finished, but if you’re trialing other distros anyway I don’t think it would hurt to boot it up and explore it (at least for a few minutes)

We can’t choose for you, unfortunately, only give you advice. My advice question is: Kubuntu and Debian (KDE Neon too, iirc) are an LTS distros, why would you chose them given your criteria?

For myself, I can recommend Bazzite or Aurora, if you are okay with using an immudable distro. They are both Fedora Atomic based, but Bazzite is gaming first, while Aurora is a general purpose distro.

openSUSE Tumbleweed is also amazing. It is rolling and generally one of the best KDE experiences you can get. It also has a snapper tool, which lets you to rollback to the state before the update or even further.