What is your favorite UNIX. Three possible categories, choose one or more: 1) Free 2) Forced to use a commercial platform. I guess that could include macOS and z/OS with some vivid imagination, maybe even NT. 3) Historical Me: 1) FreeBSD - I find it to generally be the least annoying desktop and laptop experience with admittedly careful selection of hardware to ensure compatibility. It's ideal to me for commercial appliances and servers due to the license, tight coupling of kernel and base, and features like ZFS, jails, and pluggable TCP stacks. Linux distros lost their luster for me once systemd was integrated into Debian, and that kind of culture seems to be prevailing up and down the stack in a way that I'd prefer to be an outside observer of Linux and not dependent on it for now. 2) AIX - I often see people disparage AIX but I like it. I learned a lot in my teens about C, build systems, compilers, and lots of libraries trying to port random software to it for auto-didactic reasons. It definitely doesn't feel like any other UNIX. It probably supports high core count and NUMA better than any other system except Linux, it had advanced virtualization with LPARs and containers with WPARs before most and hot patchable kernel, fully pagable kernel, lots of rigorous kernel engineering there that didn't get a lot of fanfare. SMIT is kind of cool as a TUI and spits out commands that you can learn through repetition and use at the CLI or scripting. I think it probably peaked in the early 2000s, but the memory management, volume management, and file systems all seemed pretty forward thinking up until then. I don't think SMP performance was a strong suite until it was pretty much a relegated niche though. 3) IRIX - it just screams '90s cool like an acrylic sweater. Soft real time, immense graphics support, pro audio and video features, lots of interesting commercial software, NUMA, supercomputers. I enjoy tinkering on this still, but a lot of that is due to the neat hardware. Regards, Kevin