If this breaks the AMD Adrenaline driver UI (which seems to also use QTWebEngine), you need to do it as a batch file so it runs in it's own environment. Just copy the following into a text file named "Calibre.bat" on your desktop.
Code:
@echo off
set QTWEBENGINE_CHROMIUM_FLAGS=--disable-gpu
set QT_QUICK_BACKEND=software
start "" "C:\Program Files\Calibre2\calibre.exe"
Click on this to run Calibre instead of the normal Calibre icon on your desktop.