It's not just "unsupported" machines having issues with this update, a lot of folks including myself have had it fail on so-called supported machines.Tried installing Security Update 2018-002 10.13.6 on 2008 Mac Pro running DosDude's HS patch. Update froze the system and I ended up having to restore from TM. What's the trick to get these updates installed on an unsupported machine?
BTW this is the first and so far only update that has gone sideways for me and I'm sure for others also.