You cannot natively install Game Pass on Mac, but Xbox Cloud Gaming (Beta) works in Safari or Chrome.
Before downloading, ensure your Mac meets these minimum technical specifications to avoid performance issues: : macOS 10.11.x (El Capitan) or higher. Processor : Intel Core i5 or higher. Memory : 4 GB RAM. Cuphead Mac Os Free Download
While the full game isn't free, there are legal ways to play without immediately paying, or at very low cost. You cannot natively install Game Pass on Mac,
For those unwilling to pay but wanting to satisfy the search intent, here is the exact process: here is the exact process: