Apparently Vega FE drivers don't like Windows Update updating your Win10 version to a new build.
I'm a Win10 Insider, so I get new builds pretty frequently in the fast ring. I've already gone through this one. The first time, it defaulted to Pro mode and only allowed me to switch to 17.9.1 gaming driver (was on 17.12.x before), which crashed and forced a reboot. After rebooting, it reverted to Pro mode, and then for some miraculous reason it allowed a switch to 17.21.x (but NOT 17.9.1), which worked. Thank goodness.
Yesterday I updated to 17083 which caused the same problem, but switching driver mode b0rked the entire driver install every time I did it, no matter how closely I followed instructions posted earlier in this thread.
I tried running the AMD driver cleanup utility, but that messed up something on my system preventing me from installing the Radeon Pro display drivers at all
So I ran DDU, and that fixed things allowing driver installation, BUT it apparently killed some .dll files in Windows/System32 related to the Qt framework that Radeon Pro Settings needs for base functionality (wtf). So now I need to find out how to get QtWebEngine.dll (NOT QtWebEngineCore.dll or anything similar) back on my system. For now at least the driver is working, even if I can't switch driver modes right now.
Anyone got a copy of that file handy? Or know how I can restore it?
edit: got the file, but it does not stop Radeon Settings from crashing. Not sure where to go from here. Reinstalling the entire driver package from scratch isn't fixing the problem either.