So I started with this link. However before you can follow this you need to disable system integrity protection (read about it here and here) which sounds way scarier than it is. Basically the kext we need to add so Dolphin recognizes your gc controller & adapter (mayflash or official) modifies your kernal which can be an entry point for viruses so apple makes it hard to do this. So what you need to do is turn off your Mac and then while booting back up again hold command-r. This should boot you into recovery OS, now go to utilities at the top bar and open terminal. In terminal run the command:
csrutil disable
you should see some text show up along the lines of the command running successfully. Now reboot normally and go to terminal in the normal OS and run the commands from the first link or use the installer (remember you need the download too!).
sudo cp -r ~/Downloads/SmashEnabler.kext /Library/Extensions/SmashEnabler.kext
sudo chown -R root:wheel /Library/Extensions/SmashEnabler.kext
sudo touch /Library/Extensions
Now reboot normally again and your Dolphin emulator should be able to recognize your adapter/controller. You'll want to follow the same steps earlier now to get into the recovery OS and run
csrutil enable
to turn on your protection again.
Hope this is useful to someone and feel free to copy and paste this anywhere.
this thread is great for troubleshooting