There is no “official support” for this. Is FOSS. You are on your own to run it. If my instance breaks I can’t just run to the Devs of the project to help fix it. It’s on me.
It’s a project run by two people. And to be fair to them they chose one of the most OS agnostic methods to help build it. You don’t need to use a specific distro, just tools.
You can port what’s needed over to BSD and do a PR to merge it, even if it’s just a BSD_Jails.md file. But it’s gonna take some know how.
Building a Lemmy instance on pretty much any Linux box is fairly easy and well documented though.
On a personal note, imho it does no good to be an OS evangelist. It’s as true for MacOs or Windows as it does for BSD. Use a tool for its strengths. I have BSD running my firewalls and even some storage, Linux running stuff, windows for things it excels at, and macos for stuff it works for.