Getting GarageBand on macOS Catalina 10.15.7 is entirely possible and free, though the process is slightly different than a standard download. Because the latest version of GarageBand in the Mac App Store typically requires macOS 11 Big Sur or later, users on Catalina must access the (typically version 10.3.5). How to Get GarageBand for Catalina 10.15.7
To run GarageBand smoothly on macOS 10.15.7, ensure your Mac meets these minimum specs: Garageband For Catalina 10.15.7 -FREE- Download
To download GarageBand macOS Catalina 10.15.7 for free, the most reliable method is to Mac App Store's "Purchased" history to fetch the last compatible version (typically version 10.3.5). How to Download the Compatible Version Getting GarageBand on macOS Catalina 10
If you have never "purchased" GarageBand before (even though it's free), you might not see it in your history. Borrow a newer Mac: How to Download the Compatible Version If you
In this case: