I might be scarred for life as a long time Debian Testing user, but I found that this worked approximately never. There was always some sort of dependency that was only in Unstable, and installing that would cause libc to need to be upgraded, and then your entire system broke. Even if it wasn't that severe, it probably didn't work. Windows, Mac, and iPhone users certainly don't have the problem where if they install FooUtility, it causes their computer to not boot anymore. (Unless FooUtility is malware, of course, which I didn't get a lot of installing out of Debian's repositories. Except of course that weak keygen bug... Hmm.)

(Of course, the underlying problem is that shared libraries are actually a bad idea. They were a hack for days when storage and memory was very expensive. But for some reason, Linux still uses them. New languages just compile everything into a statically linked binary, which is wonderful. I can write a Go program on my Windows machine, and with one command, compile it for a Raspberry Pi. Copy it over and it just works. Snap is also a thing that appears to work well.)

I used to use Testing and that's your problem, not the idea of repos. Both Stable and, ironically, Unstable have far fewer hiccups than Testing.

I'm a long time Ubuntu PPAs user and they work like expected, for precise reasons (the parent makes a generic consideration about 3rd party repos, so I introduce the discussion with Ubuntu).

PPAs build in environments matching the chosen distributions, so as long as the builds are properly setup and the user chooses the correct one (which is automatic, with the standard tools), dependencies will work out as expected.

The last time I had a discussion about perceivedly broken PPAs with somebody on HN, it turns out that he was abusing this system, by not using the proper suite (distribution).

I'm not sure how this works for Debian (I think PPAs also allow Debian suites), but if there isn't such [widespread] support for 3rd party repositories, then this subject should get more consideration.

Regarding shared libraries, if they wouldn't exist, operating systems would would take an order of magnitude more in space. I'm not a big fan of an 80 GB Ubuntu; if the public accepts that, that's fine, but shared libraries have a specific purpose.

I think the point is less about repositories and more about how desktop operating systems let you install any software you want, be it via package managers, Makefiles, or random binaries you get via torrent.

Install your custom stuff into /usr/local and never let the system package manager know about it. GNU Stow can manage self compiled binaries with ease.

You can package software on Linux with specific libraries: see Flatpak and Snap.

You can manage multiple versions of shard libraries as needed by different applications: see Nix.

Nix's is such an obvious and elegant solution to me that I wonder how it hasn't got much more traction.

I suspect a big part of it is people don't want to learn a subset of haskell to in order to effectively use their package manager.

Yeah, debian nowadays is much better you should try sid or buster.