Maybe somebody here knows the answer.
I have the above setup, but no sound comes out of the GB when I play a note in Logic. Be it from a USB controller or via the onscreen keyboard. Are there any settings I need to make in mGB or elsewhere?
Any help is appreciated.

pretty sure mgb is designed to be used specifically with an arduinoboy

mGB compatibility is listed as a feature on the Nanoloop site, so I guess it should work somehow. https://www.nanoloop.com/midi/index.html

(BTW: The mGB you can get from Github is a 64k file. Shouldn't it be 32k?)

mGB works with the nanoloop midi adapter. Yeah it's 64k, that is correct. It also uses SRAM so just be aware of that if you're using like an EMS cart with LSDJ on another page or something.

Does the adapter show up when you select the midi output in logic? I have a nanoloop midi adapter and can't get it to work either. I was talking to wisefire at SquareSounds Tokyo and he was saying it's way more reliable if you solder a USB cable directly to the adapter. Haven't tried that though!

The adapter seems to work fine. I can load 32k roms onto my Nanoloop One cart and it shows up as MIDI device in Logic, as you can see in the screenshot.

About the 64k: Here (https://www.nanoloop.com/one/index.html) the Nanoloop One page lists mGB as a compatible rom for the cart, but it "only" has two additional 32k rom slots. Does anybody know what that is about? I found a modified mGB on this forum which is 32k and I could load onto the cart and it seems to start up fine.

Oh yeah, in that case you're probably fine. I don't know what else it could be!