I am looking at setting up an OCSP responder using openssl and there is a minor fix that adds critical functionality for using the openssl ocsp module as a systemd service. See Fix #10682 here: https://github.com/openssl/openssl/commit/1cf20ca31bed31c0bd16c6ed1eeaa1b9580939b7
It looks like that fix is only targeted for master and 3.0.0. It seems like it would be pretty trivial to backport it to openssl 1.1.1 or 1.0.2.
Of course there may be another tool that is preferred for setting up an OCSP Responder.