cc @IvanKobzarev on the Vulkan issue.
BUILD_CAFFE2_MOBILE is for legacy caffe2 build (maybe we should consider deprecating it?). BUILD_LITE_INTERPRETER=1 is suggested for building mobile.
NNAPI is in Prototype stage, (Prototype) Convert MobileNetV2 to NNAPI — PyTorch Tutorials 1.9.1+cu102 documentation 1. @David_Reiss does it work with 1.9.1?