Developers porting Android 10/11 ROMs to older hardware in 2021 often needed to pull this file from a working device or from AOSP source code.
You don't usually "download" this file separately—it's part of the Android source code. But if you need a copy:
From a custom ROM or device vendor – If you’re building Android, place this file in:
Download your phone's stock firmware (e.g., from SamMobile, Xiaomi Firmware, or manufacturer).
Extract the system.img or vendor.img, then use a tool like imjtool or mount it on Linux to retrieve the file.