FreeBSD is a tremendous project. I've used it since the 4.x days, first for work (web/mail/database hosting, at the time) and then for personal projects.

I have a 2000-era desktop PC as a personal server that I had left collect dust until very recently after switching to Macs for daily work long ago. It was running 6.1 and I hadn't booted it in a few months shy of ten years. I booted it right up, and in an afternoon proceeded to, in small stages, update it to the latest 12.1 release, which I am running with great stability now, including live repartitioning and better use of the available disk space after going into single-user admin mode. "Recent" improvements that I've been appreciating have been a smaller/more dense console font, easier wireless configuration (it has an Atheros-based PCI wifi card), and easier and more clear package and ports management. AND it still runs fast.