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Apple’s Gatekeeper security settings for older apps. Fix: Open Terminal and type: sudo spctl --master-disable Then go to System Preferences > Security & Privacy > General and select "Anywhere."
If you have ever downloaded GarageBand with your Apple ID in the past, this is the easiest official way to get it. Apple Support Community Garageband For Catalina 10.15.7 -FREE- Download
If you already purchased or previously downloaded GarageBand with the same Apple ID: Apple’s Gatekeeper security settings for older apps
