for the macpro5,1 crowd, there is always this:
forums.macrumors.com
personally i am a mojave person... and will stay there as long as possible. i had applied this update to 2 machines but not my other two. don't use either machine that much so can't say if i've had problems with the security update.
OpenCore on the Mac Pro
This guide explains how to use the excellent OpenCore boot loader to install, run, and update the latest version of macOS on the MacPro5,1, resulting in a clean, unaltered operating system just like on a supported Mac.
personally i am a mojave person... and will stay there as long as possible. i had applied this update to 2 machines but not my other two. don't use either machine that much so can't say if i've had problems with the security update.