There’s nothing to really block much on the aur. There are some guidelines in naming and no duplicates, no maliciousness etc that are enforced, but that’s it. But anyone can upload a build script (PKGBUILD) for anything.

If you want to see how it’s done search the package name and AUR and you can see the build script right on the website.

TIL! Thank you :)

Both Slack and Spotify do provide Linux versions, even if not/less supported officially.

Thanks! I hadn't tried Arch yet, but I just saw the pkgbuild script on the site (didn't know it was there) and it makes since now :)

There are many PKGBUILDs on AUR that cactually download rpm / deb packages and unpack the binaries and deps from it.