[mtzet]

So let's focus on the case where I'm setting up a bunch of bare-metal hosts as servers. What's the value proposition of using FreeBSD over Debian/Ubuntu if we're not counting familarity?

Either experience will be CLI first, so this is a tie.

ZFS integration is one point. If that's important to you, then you'd want to pick a distro like Ubuntu with first-class support. All major development happens on the Linux on ZFS branch as far as I understand, so this should be okay.

As the original post points out, FreeBSD used to have unique features as selling points: zfs, dtrace, the network stack (before SMP became ubiquitous?), kqueue, jails. I'm sure there are others. But these days it seems Linux has caught up with developments like ebpf, cgroups, namespaces and io_uring.

I'm sure the fragmented nature of Linux means that some of these low-level techs are easier to use on FreeBSD. The counterpoint is that the higher-level stack is more well-supported on Linux. You may not have to care too much about the details of namespaces and cgroups if high-level docker/kubernetes/... tooling works for you.

What am I missing?

[karmakaze]

That's a great summary that details what I was suggesting.