Yes, you’ll certainly have to resolve this issue with not being able to compile a minimal HDF5 program before compiling OpenMC. But that is obvious.
This may help you out:
IMO it’s better to just not use conda if you don’t have a need to install multiple versions of stuff to the same system, although that is not a commonly held sentiment. If you’re on macbook, I would brew install hdf5 and the other dependencies.
If this continues to give you trouble, you may want to consider installing OpenMC using docker.