There are too many articles to make Apple Magic Keyboard 2 to work on Windows 10 with Function keys (volume etc).
None of them explain how to do it on windows machine that is not running o non-apple hardware and if there are - none of the method worked.

Simple steps, without a foreplay:

• Download brigadier that is a script which downloads bootcamp bundle from Apple, basically just finds a path on CDN:https://github.com/timsutton/brigadier/releases
  
• Find the lastest and gratest mac product model IDs, I chose iMac 27-Inch „Core i9“ 3.6 (5K, 2019) - iMac19,1 (https://everymac.com/systems/by_capability/mac-specs-by-machine-model-machine-id.html)
• Download the bundle: brigadier.exe -m iMac19,1 (please note there is a dependency on 7zip to be installed on the system)
• In my case bootcamp 0.61-97204 was downloaded, so crawl to: „BootCamp-061-97204\BootCamp\Drivers\Apple\AppleKeyboardMagic2“, right click on „Keymagic2.inf“ → Install.
• Reboot

Magic, sound controls work as expected, fn key switches to functions etc. No changes in device manager device name, but that doesn't bother me.