I managed to play some rounds, it works fine on mGBA just as you said. I also tried to play it on VBA and no$gba but I could see nothing in debug messages.
I don't have experience with butano, but I took a quick look through the code and found out that log function has different implementations separated by an #ifdef statement depending on the target emulator. Not an advised opinion, but I think you should have a different build compatible with each emulator you want to display log messages in. Hope you can get something useful from these!