Often apt's versions trail behind the newest versions. There are some good reasons for this, but it can get in the way sometimes.
I have had to ad a lot of PPAs to get some of the software I wanted. The Aurora channel PPA for Firefox stopped getting updates at one point (they discontinued it), and I didn't realize until a few versions later. I don't think any of these package managers have that problem figured out, but PPAs are commonly maintained by third party community/unofficial folks. I had the same problems with Arch's AUR.
I believe it's fixed now, but for a long time Steam required a lot of 32 bit libraries, which meant two versions of several dependencies were installed on my machine.
Additionally we were using an older version of Ruby at work which required OpenSSL1.0 for certain libraries, and a Ruby upgrade (from an old version to a less old version) broke my development environment.
Not that the others are perfect. Just for example the Spotify snap package from the software center doesn't even work. The Deb had problems on my machine which I couldn't resolve. I finally installed Flatpak to get a working version.
Well, I have found some strange, out of common, software - mostly comercial stuff - which doesn't have any .deb available nor ppas, nor nothing.
It is clearly a decision from somebody who said "no, we are not spending hours packaging our app, if they want it, they will try to install it with the methods we will provide"
Kind of nonsense, except that if you're in Linux looking to install a comercial app, special snowflake, is probably because you have zero chances to do otherwise, then you bit the bullet and try whatever crazy method to deploy their app they have put in place.
Most common stuff I found: - Just download my zipped binary, you know how to deploy it - Just run this command line, "sh something" giving it root credentials to run code from the Internet (YEAH I KNOW TOO, as much insecure as it gets)
Having said that, many comercial apps are there for to be easyly downloaded as .debs (they should just install with a GUI right out from the link, in old-Ubuntu behavior). Or they even offer you detailed instructions to configure a ppa (to manually install with apt).
Heck, nowadays it is common sense and good netiquette to make your installation scripts in the downloaded .deb to just deploy the ppa for apt, so next upgrade happens automatically.
If you ask me and I wouldn't dreaming to control the app-deployment infrastructure in Linux, I would say "yeah, you need to contact EVERY software not providing the .deb format and start working with them, providing them free support, even free scripts to handle the packaging"
I remember in the 90s, there was LOTs of shareware because Microsoft knew this stuff from the 70s and 80s: if you want you're software in use, you need to talk directly with those who could probably use it.
No, links hanging in some flashy website won't cut it, nor repos in github half sharing some code.
