Using UEFITool
git clone the repo:
git clone https://github.com/LongSoft/UEFITool.git
build the tool:
cd ./UEFITool
/usr/lib/x86_64-linux-gnu/qt5/bin/qmake /uefitool.pro
make release
extract vga bios:
open the original bios rom with UEFITool
search for text "VGA Compatible BIOS" (uncheck unicode) - File -> Search (This will highlight the raw section)
right click highlighted raw section and select Extract Body.... Save the extracted file as vga_bios.img.