I eventually fixed this problem by upgrading CUDA from 10.1.168 to >=10.1.243.
An excerpt from the CUDA release notes in case other PowerPC users stumble upon this problem:
“The cuSPARSE generic APIs are currently available only for Linux x86_64 (AMD64) systems. Using these APIs on any other systems will result in compile-time or run-time failures.” [1]
[1]  https://docs.nvidia.com/cuda/archive/10.1/cuda-toolkit-release-notes/index.html#cuda-u1-libraries-known-issues 11