The command you most likely used is freebsd-update[0]. There are other ways to update FreeBSD versions, but this is a well documented and commonly used one.
> I don’t recall having to reboot — might have needed to.
Updating across major versions requires a reboot. Nothing wrong with that, just clarifying is all.
> Most people who use containers a lot won’t find a home in FreeBSD, and that’s fine. I hope containers never come to the BSD family.
Strictly speaking, Linux containers are not needed in FreeBSD as jails provide similar functionality (better IMHO, but I am very biased towards FreeBSD). My preferred way to manage jails is with ezjail[1] FWIW.
> But then, most people who use FreeBSD know you don’t need containers to run multiple software stacks on the same OS, regardless of needing multiple runtimes or library versions.
I completely agree!
0 - https://docs.freebsd.org/en/books/handbook/cutting-edge/