Hello and welcome! I would also suggest one of the *BSDs if you want a more UNIX-y experience. But you'll probably find that they have converged a lot with Linux, they're all fairly easy to use.

If you really want to do something different, let me suggest OpenIndiana, a Solaris-derived operating system. Solaris is where ZFS, Zones (like jails or containers) and DTrace (great kernel debugging tool) came from, so you might want to give it a whiz in a virtual machine or something. And it's still actively developed.

Best of luck in whatever you decide to do, and feel free to ask for help in the forum or IRC!