ekze

You forgot the one important step to get this card working on Windows! I have a Vega M GL card, which doesn't support the "optional" drivers and wanted the CEMU async shaders on my laptop.
 
"I did find a bypass that will let me install the optional drivers on my card though.
 
I looked through the INF files of both drivers and noticed the March drivers have this line
AMD694E.1 = "Radeon RX Vega M GL Graphics"
AMD694E.2 = "Radeon RX Vega M GL Graphics"
(as well as some other lines relating to this)
whereas the April Driver is missing these lines. However, editing the INF files means that the security certificate becomes invalidated.
 
Currently the best bypass to install the unapproved "optional" drivers is to first start the installation of the "Optional" Drivers until you hit the error screen, then go to Device Manager>Display Adapters>Radeon RX Vega M GL>(right click)>Update Driver>Browse my computer...>Let me pick from a list...>Have Disk>Browse...
 
Then browse to This PC (left side)>Local Disk (C:)>AMD>Win10-Radeon-Software-Adrenalin-2020-Edition-20.4.2-Apr23>Packages>Drivers>Display>WT6A_INF>C0354308.inf
 
Then hit OK, then find "Radeon RX Vega". It will say "Installing this device driver is not recommended...", just hit yes. 
 
Now the GPU identifies as "Radeon RX Vega" instead of "Radeon RX Vega M GL Graphics", but everything else seems to work fine. And now I have Vulkan 1.2 support."
 
Try this and I think you have about a 70% chance of getting it working on Windows.

You're lucky to have DVI output. Newer cards don't have that, so you have to buy expensive DP-DVI active converter. (They have 3xDP usually, so you're fine as long your monitor has DP)