> Surprised about FreeBSD. My experience is that porting Linux software is usually pretty easy as long as it's not using some Linux-only feature (io_uring for instance).

I'm not sure why you're surprised, the parent of you comment clearly stated

"on FreeBSD you often run into systemd dependencies or other non-posix behaviors"

which means, software written for Linux often uses "Linux-only features" such as systemd and other non-posix dependencies that are foreign to the BSDs and traditional UNIX. Thus, it shouldn't be surprising that Linux software is hard to port to the BSDs.

Linux used to be a pretty good UNIX, I'm not sure what it is now.