How to extract the minimaps from your game files and save them as images.
Open e.g. "Chora". The file "Chora_Minimap.uasset" contains the texture for the ingame minimap. The problem is that the filetyp "*.uasset" is an Unreal-Editor binary file and no simple image.
Let's find a viewer/converter...
Download Gildors UE Viewer and extract the ZIP-file to your preferred location. There's nothing to install.
Change the path to the game files like shown above and deselect everything beside "Textures".
Click "OK". You'll see a directory tree. Browse the folders for files with "minimap" in it.
The "Open" button opens a viewer. Attention: Don't press ESC but "O" to get back to the tree view.
The "Export" button will save the file as TGA-Images to the folder "UModelExport" located in the directory of "umodel.exe".
From TGA it's just a small step to any other image format. Use Gimp, Irfanview, Photoshop... you name it!