ruby-install | Installs Ruby , JRuby , Rubinius , TruffleRuby or MRuby

So, it turns out that I had multiple versions of Bundler installed on my machine and, somehow, two of them were simultaneously set to the default version. Manually finding the installed versions, deleting them and then reinstalling the desired version seemed to fix the issue. The key is using a Ruby manager (RVM, rbenv, etc.) and ensuring that any installation of a Ruby version and/or gems are done at either a system level or inside of a project as required.

This is not an official solution. I'm sure the rbenv devs are working on an actual solution but this workaround should help others who are setting up their ruby environments on the new M1 chips for Mac.

• Make sure your Terminal is using Rosetta. You can find how to do that using Google.

• Uninstall your current rbenv following these instructions Removing rbenv. Be sure you also remove all the downloaded versions of ruby if you have any (minus the system default) located in /Users//.rbenv/versions/.

• Uninstall the ARM version of Homebrew with: /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall.sh)"

• Install the x86_64 version of Homebrew with: arch -x86_64 /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"

• If you run brew install rbenv should produce output saying "Error: Cannot install in Homebrew on ARM processor in Intel default prefix (/usr/local)!". This is expected.

• You want to tell brew to install the older architecture x86_64 arch -x86_64 brew install rbenv

• Then finally install the version you want using arch -x86_64 rbenv install x.x.x (x = some number i.e. 2.7.2)

From there you just need to remember to tell brew arch -x86_64 when installing other versions of Ruby.

Once an actual fix comes through you'll be able to switch back to the newer architecture and not have to use the arch argument. You also don't have to do this all the time with brew either, just rbenv.