Garageband for OS 10.15.7.

They're not "our" updates since we're all just fellow users here. Apple does not participate in these forums.

As to your question, if you're now trying to download GarageBand, then the updates have indeed made it incompatible with your version of macOS and there is no fix if your MacBook is not capable of running macOS 10.14 Sonoma.

Regards.

It is unclear what the problem is.

You can drag garageband to the trash and re-download it from the App store.If that works, you can empty the trash.