setting the MGF hash to a different value other than the regular hash with openssl for PSS signatures
Meta: since this is about using a tool not the underlying algorithm/math AIUI should be security.SE instead. If anyone can and wants to migrate feel free.

Per 1.0.2 source, -sigopt rsa_mgf1_md:name where name is the name of a hash available to EVP_getdigestbyname -- that is, implemented and not #if'ed out by default (MD2) nor manually.

For FIPS mode if relevant, I think you can set a non-FIPS hash but then the operation using it will fail, but I don't have a FIPS build set up to test.