Modern macOS uses "Gatekeeper" to verify that apps are signed by certified developers.
: Retained the high-resolution editing capabilities introduced in the earlier 10.1 series, allowing for 4K video exports. Legacy OS Compatibility
Strictly speaking:
If your Mac is too old even for High Sierra, you can still run iMovie 10.1.16 using (like DosDude1’s patchers). But a lighter alternative is iMovie 9.0.9 (iMovie ’11), which still runs on OS X Lion or Mountain Lion.
Modern macOS uses "Gatekeeper" to verify that apps are signed by certified developers.
: Retained the high-resolution editing capabilities introduced in the earlier 10.1 series, allowing for 4K video exports. Legacy OS Compatibility
Strictly speaking:
If your Mac is too old even for High Sierra, you can still run iMovie 10.1.16 using (like DosDude1’s patchers). But a lighter alternative is iMovie 9.0.9 (iMovie ’11), which still runs on OS X Lion or Mountain Lion.