Just FYI, your queries in this thread led to the finding that one module was returning cepa(0) values that included singles and another excluded them. (Disscussion Naming considerations for cepa(0) if curious.) The upshot of it all is that once this code is merged in, energy() calls to lccd will return linear coupled-cluster doubles (no singles) and lccsd will return linear coupled-cluster singles and doubles (conventional integrals, RHF only). cepa(0) will just be an alias to lccsd, and higher-level cepa methods will continue to include singles.
So for your purposes, you’ll be back to lccd calls where you started. Sorry for the detour, though there really are many things better arranged under the hood because of it.