I need to install GarageBand on Catalina - where is the download link? Is there a way?

GarageBand is only available from the AppStore, since Apple moved it to the AppStore. All download links to updaters have been removed from Apple'S download page.

And you can only purchase applications from the App Store, if the App Store still offers a compatible version for your system. On older system versions you can only reinstall applications you purchased previously.

if you ever purchased GarageBand from the AppSore with your AppleID, and you are seeing it in your Purchase list (the fourth tab of the AppStore) you should be able to reinstall it from the Purchase tab.

Keep in mind—-If you have NOT had it under your Apple ID before then a clever workaround is to sign out of the App Store, have a friend who HAS had it before sign in with their Apple ID, download the last compatible version, then sign out. GarageBand remains on your computer after they sign out.

There is no easy way.

If you bought it from a private party they may be able to log into the app store and get it.

The new norm for Apple is you have to keep up with its latest OS, otherwise you are on your own with those software.