That said, Swift and SwiftUI is super nice, so I know they know how to make great software for their OS-es. Almost. Once they fix XCode.
100%! Everyone repeat after me: "macOS Is Not A Server OS"
macOS is approximately the worst OS you can run a server on:
1. It is buggy. We had a bug in Sonoma where our CI machines would freeze on some filesystem access. The bug was fixed during Sonoma's lifetime... but only released in Sequoia. Before that we had a rare bug that plagued us for years (once every few months across several CI machines) where a process would fail to execute with "/bin/sh: cannot execute binary file", indicating an erroneous ENOEXEC from the kernel (that bug quietly disappeared)
2. It has no LTS version. See above filesystem hang. Want a fix? Cool, it comes only in the next major OS version, along with a host other changes you didn't want, and new bugs! (see point 4 below)
3. It is just poorly documented. Apple's doc are awful, poorly searcheable, they will change things and not document it, you're left with the community trying to reverse-engineer everything (I cannot recommend eclecticlight.co enough!)
4. It's just bloated with cruft for consumers. Upgrade to Sequoia 15.3? You got a free download of "Apple Intelligence" models, there go a few GBs! Again rely on the community to come up with the magic settings to disable stuff.
Ask me how I feel about macOS as a server.
(I lament the death of XServe, which could've driven more server-focused software quality)
It does not matter, Swift server-side can run (and be built) on Linux (or Windows BTW, or even embedded platforms (a subset of the language anyway))…
They have a lot of server-side projects going on. They are also increasingly using Swift on the server themselves (not on macOS).
Finally, small nitpick, but it shows you don’t care, it’s written Xcode.