This is a "one size fits most" file. It contains multiple Device Tree Blobs (DTBs) that allow the software to communicate with various hardware configurations. Key Features of EmuELEC 3.9
This was the last 32-bit release of EmuELEC. Starting with version 4.0, the project transitioned exclusively to 64-bit architecture. emuelec-amlogic-ng.arm-3.9-generic.img.gz
This version introduced several refinements that made it a fan favorite for stability on older hardware: Releases · EmuELEC/EmuELEC - GitHub This is a "one size fits most" file