This is a minified version of nRF5_SDK_for_Thread_and_Zigbee_2.0.0_29775ac it is only sufficient to compile the examples in the top repository : https://github.com/nRFMesh/nRF52_Mesh
for any other development, get full version of the SDK from official nordic website https://www.nordicsemi.com/DocLib/Content/SDK_Doc/Thread_SDK/v2-0-0/index