This guide shows how to set up an old Ruby + Rails environment on a modern macOS (Apple Silicon).
As per October 2025, this works on an M1 MacBook Pro (2020) on macOS Sequoia 15.6.1.
As per January 2026, this also works on an M5 MacBook Pro (2025) on macOS Tahoe 26.0.
This is what you’ll end up with: