» file ${which open}
/usr/bin/open: Mach-O universal binary with 2 architectures: [x86_64:Mach-O 64-bit executable x86_64] [arm64e:Mach-O 64-bit executable arm64e]
/usr/bin/open (for architecture x86_64): Mach-O 64-bit executable x86_64
/usr/bin/open (for architecture arm64e): Mach-O 64-bit executable arm64e
Whereas on Linux it is a shell alias. Doesn't appear to be universal either (doesn't exist on Arch, for example). It was a recent change too, added to Debian 11 (released 2021), which is years after it was added to Murex.As an aside, I wouldn't be at all surprised if the `open` alias was added to Debian to copy (and I mean this affectionately) macOS. Otherwise `xdg-open` might have just been called `open` from the beginning.