If you want to use an external or virtual camera, Canon EOS for example, you should disable codesign for Discord App.
sudo codesign --remove-signature /Applications/Discord.app/Contents/Frameworks/Discord\ Helper\ \(GPU\).app /Applications/Discord.app/Contents/Frameworks/Discord\ Helper\ \(Plugin\).app /Applications/Discord.app/Contents/Frameworks/Discord\ Helper\ \(Renderer\).app /Applications/Discord.app/Contents/Frameworks/Discord\ Helper.app
Restart Discord and you will see more camera sources than a default camera.
