Xfce does not get updated often, so by that definition it is the most stable.

It’s also pretty stable from the perspective of not crashing, but I can’t say I’ve had much trouble with KDE either.

Stable as in the UI doesn’t get changed often, or stable as in unlikely to crash?

I’m very confused about what you’re asking in your post. You only want “bleeding edge software”, but want it to be stable? Those are competing ideas. Also, are you talking about “bleeding edge” for the desktop, or the kernel? If the latter, then why are you choosing Ubuntu 20.04?

Stable as in rarely crashes, or stable as in rarely changes over the years?

The LTS versions of Ubuntu are stable in the second sense, they get ten years of support but you’re stuck with old versions or (stable) programs in exchange. I also have not seen any of them experience a fatal crash, too. So stability isn’t the issue, its more about what you want to do and compatible with most recent versions of software.

Is this a joke? Manjaro unstable branch sounds like unstably thing to find in the Linux universe.

Go for fedora, it’s the only well known distro with newest software, stable and good community support.

This has to be a troll post

I’d probably say XFCE. Ultimately, all desktops are pretty stable, except when it comes to Wayland support. You are very unlikely to have issues with any DE on X11, (except the fact that any X11 issues on GNOME and Plasma might have been overlooked) but if you’re talking about Wayland, then GNOME will be your safest bet.

I have a good experience with GNOME and XFCE. XFCE is the most stable as in no crashes, GNOME froze on me once and only once.

KDE was a bad experience for me I had to keybind kquit krestart because of how often it froze.

Not to say KDE is bad, something about my setup didn’t play nice.

XFCE works for me, but I’ve heard that LXDE is pretty good too.

You can pick any bleeding age distro which allows locking your package versions, but as others have said, you might be asking for competing ideas.

However, if you have time to spare and want a smooth forehead: NixOS. You can install the stable version and then declare that every other package you install comes from the unstable branch.

sudo nix-channel --add https://nixos.org/channels/nixos-unstable nixpkgs-unstable

/etc/nixos/configuration.nix

{ config, pkgs, lib, ...}:
let
   nixpkgs-unstable = import  {};
in
{
  # Stable X with KDE
  services.xserver.enable = true;
  services.xserver.displayManager.sddm.enable = true;
  services.xserver.desktopManager.plasma5.enable = true;
  # other packges from the unstable channel
  environment.package = with nixpkgs-unstable; [
    firefox
    chromium
    libreoffice
    # ...
  ];
  # The rest of the stable stuff
}

https://nixos.org/manual/nixos/stable/#sec-installation

I am already sorry for the pain you will have to endure trying to find the proper documentation, but I truly think this is the best solution for your usecase. Good luck.

Feel free to ask for help on Matrix chat or the forum.

Again, apologies.

You want bleeding edge but are moving to Ubuntu 20.04, which was released in 2019 with a 2025 EOL? No DE from that release’s repo will be bleeding edge. You can manually install the newest releases of software you want, but that’s not really a “just works” solution either. You’ll run into dependency hell at some point. I’m not really sure what you’re going for. But as far as a stable DE goes, and if that is the main concern as implied in the title, XFCE has been pretty darn solid for me.

Xfce. I have used it daily for at least 14 years and it has never crashed on me. I often forget it is even there, it is so reliable.

Vanilla gnome should cover your needs.

You want a solid material and 4 legs you probably want the legs on a solid surface too.

Any will do. I think all the major desktop environments are fairly stable. (If you you use the stable releases.) If I encounter bugs, it’s mostly in user software or hardware/driver related issues. I’m not sure if I would switch to Ubuntu 20.04, though. And if you already do all the stuff with the third-party sources, bleeding edge applications, I’d say the one or two annoying bugs in KDE over the years are the least of your concern.

I usually recommend getting a distro that somewhat aligns to your personality or usage scenario. But I’m not sure if it applies to you, since you’re set on mixing it with other sources and that will make the benefits you get from distro maintainers packaging the software meaningless. Maybe choose the recommended distro for your ‘third-party package manager’ and either of the destop environments it has good support for.