Nit pick(s)
I would say the core BSDs (Free/Net/Open) aren't rival sects, they're more different emphases. Free concentrates on running efficiently on mainstream hardware with lots of packages, Open focuses on security, Net wants to run on everything including toasters, bionic artificial limbs and engine management systems. Dragonfly is/was schismatic from Free.
minix & xv6 were pedagogic (as was/is Xinu which didn't get mentioned), so a different game.
Differently different, HURD and L4 are about microkernels, which arguably Are Not Unix Anyway.
Plan9 and Inferno are by definition Not Unix, being intended as research into what comes after Unix.
x7/86 seems to be an exercise in pure nostalgia.
So the only real division is between those Unices with Bell Labs ancestral DNA, and Unix-alikes. Even then, there's been so much cross fertilization that the distinction is very blurred.
On my SOHO network all the servers are FreeBSD (as is the OPNsense firewall/router) , the desktops are 1 each FreeBSD, macOS(*) & Linux, the laptops are 1 FreeBSD, 2 Linux & 1 ChromeOS, and the phones and tablets are all various Androids. No burning at the stake in this house.
(*) Or however it's capiTALisED this month.