FreeBSD 13.0
FreeBSD is such an excellent operating system, I applaud all developers and users that have kept it going all these years.<p>I've been toying around with it in a virtual machine since 13.0-RC2, in many ways it can feel like a foreign system (compared to my Linux background), but there are a lot of nice things that also make it feel "greener" on the FreeBSD side. It's honestly hard to understate the value of boot environments and the boot loader's capability to swap between them or even roll back to a spool checkpoint. It makes almost all upgrades and system changes risk-free.