Here’s something the tutorials don’t tell you, but that is kind of important: Flutter plugins add their own CocoaPod dependencies to the iOS project. This is why the installation instructions for Firebase tell you to skip through everything in the iOS installation after you install the GoogleService-Info.plist file. The rest of the installation gets handled by the Flutter plugins for Firebase.
I hate apple for not managing the dependencies chains. I really kind of can’t believe how bad it was a couple of years ago. That CocoaPods exists is an embarrassment.