For all guys with problems on the new Asrock BIOSes (for this board, and for other Asrock boards), add in Clover's config.plist,
under ACPI\DSDT\Patches the following patch (I already posted my patch in the General Z390 thread):
<string>Fix AsRock Z390 BIOS DSDT Device(RTC) bug</string>
The problem his an uninitialized variable in Device(RTC) that makes OSX DSDT parser freak out.
I am quite sure AsRock will eventually fix this, but for now, it is a usable solution.