If the App Store method fails, your last resort should be reputable digital preservation archives rather than random file-sharing sites.
If you have acquired a trusted DMG file for GarageBand 10.3.5, here is the standard installation process: Download the GarageBand-10.3.5.dmg file. garageband 1035 dmg link
Older builds often run more efficiently on older Intel-based Macs compared to modern, resource-heavy releases optimized for Apple Silicon. The Risks of Third-Party DMG Download Links If the App Store method fails, your last
: Apple occasionally offers GarageBand as part of its software lineup on their official website, but typically, you'd still use the App Store for updates and downloads. If the App Store method fails