Same, once you installed 18.5+ drivers, you'll need to reinstall your whole Windows Installation, even if you DDU + AMD's Clean Install utility in safe mode, you will still black screen. Then use an older driver like 18.2 and NEVER update your AMD driver again till this problem is fixed.
I've been lucky, well sort of.
18.6.1 almost works. I mean, I can browse the internet and do basic stuff and it works. If you try playing games (in my case mostly EU4) the computer will reboot itself. no warning no nothing just reboot.
Tried the last ones also (a couple of days ago 18.7.1 came out) and still the same problem. completely black screen.