If you are on a modern version of macOS (like Monterey, Ventura, or Sonoma), you should generally download the from the official XQuartz.org site. However, if you specifically need 2.7.7:
If you’re on , install XQuartz 2.8.x instead – 2.7.7 will fail to start due to missing system frameworks. xquartz 2.7.7
Check your current version: