Hi, in RetroArch 1.7.3 for Windows 10, the nSide Balanced Core does not load the Super Game Boy games with the instructions provided in the docs section.
However, if the file “sg1.boot.rom” is renamed to “lr35902.boot.rom” it loads.
In my computer the Super Game Boy games run very slow and the sound is garbled, I don’t know if this is related.
I hope this info is helpful.