Hi there Abz,
I recently switched to using the Gambatte plugin for GB/GBC as I like the accuracy, but I've noticed a problem with it. After loading a game the message "Gamecube Controller configured in port 1" pops up on the bottom of the screen for a second, disappears, then returns again and again and again. It's got nothing to do with that controller specifically, whether I use GC, Wii, classic, it all has the same behavior - in fact it responds to gameplay, in Kirby's Dreamland for instance it happens every time you interact with an enemy. Have you been able to test it yourself? All Retroarch cores display the message but this is the only one where it keeps happening.
I've experimented with different control bindings but I just end up locking myself out and. as far as I can tell, you can't just turn off the messages. I remember in previous cores the input messages wouldn't appear at all, though, so is there any chance you have any older Wiiflow plugins for Gambatte? According to the menu it's Gambatte (v0.5.0) from the 1.3.4 set, which I think is the most recent from your 2016 pack. Of course, if you have any other suggestions they're more than welcome. Thanks