If you are starting to develop with a new Apple M1, follow this article to install fastlane.
Please, follow the instructions in the post Apple M1 – Install cocoapods.
After installed Xcode and iTerm running with Rosetta:
WARNING! Until now (02/2021) fastlane isn’t working correctly with HomeBrew in M1.
Let’s install fastlane with gem command:
sudo gem install fastlane -NV
Probably will be installed the command line tools.
To fastlane run without errors, you need set:
Xcode -> Preferences -> Locations -> Command Line Tools
Done, now you can run fastlane commands!