Linux

I know you already got another answer, but - it's very rare that any software for Linux exists that is both 1) not present in the official Arch repos, and also 2) not packaged by a user for the AUR.

Probably 99% of what a typical user (I know we all define that differently) will want doesn't even require AUR access - it will be in the official Arch repositories and will be up to date to within a few weeks of release.

There are some potentially substantial downsides to the AUR (it's the Arch USER Repository - so these are not official arch packages) but IME the real world problems are minimal. I would suggest anyone who is new to the Arch way of distributing software should hit up the relevant page on the Arch wiki and make up their own mind before using the AUR - but it's about being aware of what you are doing more than it is a real warning, if that makes sense. I suspect few Arch or Arch-based users don't have at least a smidgen of AUR packages on their system. (Edit: That page is very thorough. I think it makes installing from the AUR sound much harder than it needs to be. For most people the command is just "yay -S packagename." There are gui options that handle all packages including AUR, and yay is not the only cli option, either.)

Interestingly, there are some AUR packages that work by pulling down the deb and deconstructing it for installation on your system - AFAIK it can be that, RPM, a true "compile from source" situation, or I'm guessing some AUR packages are deconstructing snaps\flatpaks\appimages during the install. Whatever the origin of the files, they include a pkgbuild file that tells your system how to either compile or deconstruct and install the software.