Is this specific to Debian?

https://www.freedesktop.org/software/systemd/man/latest/mach...

https://dbus.freedesktop.org/doc/dbus-uuidgen.1.html

Nope, but Debian does use systemd by default so it's there.

I'm running Arch Linux and /etc/machine-id is present.

There's also an optional /etc/machine-info file that could exist. It's not a part of systemd and won't be created by default. It's more of an informal way to have details about the system in 1 spot. It was more popular when provisioning bare metal servers but still has value in the cloud. You can have key / value pairs on who to contact, where it's located, what type of machine it is, etc..

FreeBSD has it as well.