As another user mentioned, package managers are specific to distributions rather than DEs. The main difference between them is that they’re developed by the respective distribution teams, but there are some practical differences too. For example, apt supports versioned dependencies while pacman doesn’t because of the different distribution models between Debian and Arch (monolithic vs. rolling release). This affects their dependency resolution strategy with each being better suited for it’s respective distribution.

To address your point about package managers being the main difference between distros, this isn’t quite true. As mentioned, different distros have different distribution models, priorities, and overall biases/opinions that affect the user experience in a variety of ways and make them better suited to different use cases. I would never dream of putting Arch on one of my servers in the same way that you’d probably never catch me installing Debian on my gaming machine.

I wouldn’t worry too much about the package manager, just worry about whether the distro has a good package repository. If it has all the software you want to use, then use it. In my opinion, most package managers (dnf, apt, pacman, xbmp) are basically the same, and you would only notice a big difference if you ever tried to make your own package for your own software.

That said, a few package managers are very different from all the rest:

• Crux OS “prt-get”: simple and stupid: just downloads and installs tar archives.
• Gentoo “emerge”: builds all software from source code when you install it. This provides some guarantees that the source code was not tampered with by the distro maintainers, this is great if you need to review all of the source code that is running on your system, but terrible for most people who don’t want to spend so much computing power on compiling stuff every time you do a software update.
• Nix and Guix: creates its own blockchain-like database of isolated package dependency chains on your system, allowing you to instantly roll-back to the previous set of installed packages if you ever install something that breaks your system. It also guarantees that the software can be checked bit-for-bit (using SHA hash) traced back to the exact version and dependencies of the source code that built it. Nix and Guix packages also live peacefully side-by-side with any other package manager since all Nix/Guix apps are completely self-contained within its own database. In a way, it is sort of like one big AppImage or Docker container, but you can just keep adding or removing stuff to it as often as you want.
• Silverblue, SteamOS, VanillaOS, BlendOS, CarbonOS: distributes “immutable images,” so it is impossible modify the operating system at all. Updates will ship an entirely new operating system with all packages built-in. However you are allowed to install software into your home directory, and you can install FlatPacks and AppImages. This provides a great deal of security in exchange for a tiny bit of inconvenience.

My personal preference: I use ordinary Debian or Ubuntu to install the critical software that needs to be stable and reliable, and I use Guix OS on the side to install the bleeding-edge things that might break a lot.

Oh no, there are 5 package managers out there and they’re all wildly different

I know! I’ll make a standard, universal package manager that’ll be better than all the others that everyone will use!

There are now 6 different package managers

The package manager is really only a small part of the story.

A distro at the end of the day is a API/ABI platform. What makes Debian what it is, is that it has a specific set of old unmoving packages. What makes Arch is that it has the latest APIs always. And everything in between like Fedora.

So even if Fedora used dpkg it wouldn’t change anything, you can’t use its packages on Debian.

As to why so many exist… well a lot of them suck in their own unique way.

Diversity generates competition that drives innovation. Also, people mostly work on what they like and use what they like. Although it certainly spreads resources on duplicate projects, you can’t force people to work or use your personal favourite. You’ll get used to it.

Because linux runs on an incredible amount of platforms with an incredible amount of hardware targets and platform goals.

It runs on every supercomputer and every raspberry pi and every android phone, as well as most web servers and almost every steamdeck.

Use cases are so dramatically different there will always be multiple distributions with their own needs for package managers.

Some differences can be explained. Pacman was created after the Debian package manager (I guess that because Debian is older than Arch) . It is justified because Pacman is faster than Apt. But its too much work to replace Apt by Pacman comparing to the benefits.

But in some cases I don’t know why. As instance I wonder why a distro, such as Void, created its own package manager instead of using the Alpine one. If Alpine is younger than Void, invert the sentence of course.

Some package managers do have differences that justify a separate project (nix, gentoo’s portage, etc).

For others, sometimes package managers are very similar feature-wise. But some developers would rather remake the thing because they would understand their code a lot better than someone else’s. Or because it would be far easier for them to customize rather than extend another project.

Imo it is developer laziness. Being able to use other people’s work is a valuable skill. But then again, this is open source, and people are free to develop the software they want the way they want.

Using Arch in a distrobox, no difference, but the AUR is convienient.

I don’t think package managers are DE-only but rather depend on the distro

Imagine having only one option, and that option is dnf. I’m out. I don’t want Linux anymore.

Are they so different that it’s justified to have so many different distributions?

Linux isn’t a project its a source compatible ecosystem. A parts bin out of which different people assemble different things. The parts being open source means you don’t need anyone’s permission or justification to make something different out of them.

From these many and varied efforts comes life, vitality, interest, intellectual investment. You can’t just take the current things you like best and say well what if we all worked on THOSE when many of them wouldn’t even have existed save for the existence of a vital ecosystem that supported experimentation and differentiation.

If we really believed in only pulling together maybe you would be developing in cobol on your dos workstation.

Convenience/ease of use; There’s a little caveat that only “true linux users” are able to notice, tho –

… compiling is, and always will be, the best option.