Before attempting to install via a DMG or the App Store, ensure your Mac meets these specs:

, finding an official DMG for version 10.2.5 requires specific workarounds. Apple Support Community How to Get iMovie 10.2.5

: If you have previously owned or downloaded iMovie on any Mac, you can often retrieve version 10.2.5 on a Catalina system by: Opening the Mac App Store and clicking your profile name.

: On Intel-based Macs with integrated GPUs, this version is noted for running smoothly, though some users on older systems report occasional crashes during long projects. Pros and Cons ICS 1-to-1 - iMovie - Google