iMovie 10.2.5 is frequently the "last compatible version" offered to users who cannot upgrade to the newest macOS.
: Create stunning cinema-quality films with video from iPhone 6s or later and other Ultra HD cameras. imovie 1025 dmg upd
If you have a slow internet connection, you might want to download the DMG once and install it on multiple Macs without re-downloading. iMovie 10
While 10.2.5 was a minor patch, it built on the 10.2 series which introduced: Big Sur UI Refinements: imovie 1025 dmg upd
For security, run this Terminal command after downloading any iMovie_10.2.5.dmg :
Before updating, always copy your "iMovie Library" folder to an external drive. Updates sometimes prompt a library database upgrade that isn't backwards compatible.