I recently bought a BIOSTAR RADEON RX 550 for a MSI Socket AM4 B450M PRO-VDH MAX motherboad, with AMD Ryzen 5 2600 3.4 GHz Six Core and Corsair Vengeance LPX 16GB DDR4 memory. My monitor is an LG LCD LED 21.5'' E2242T-BN, connected using DVI-D. My previous card was ATI Radeon HD6670 1GB DDR3 PCI-E...
As you can see on the following video, right after I install the Radeon software, the screen goes blank - no signal. The system still works but not the screen. I have to enter in safe mode and remove the driver in order to use Windows.
I tried amdcleanuputility.exe and DDU without luck.
I would suggest you try the 20.11.2 whql driver first, if the same happens then try turning off pc and restart to see if the driver install continues.
I tried the whql version and also older versions (I also tried the very first version available on the old download page), the behaviour is exactly the same.