Are you looking for award or upgrade space? For award space (which AFAIK was never on EF for DL), in principle what DL releases to partners should be a subset of DL's low award space for its own FFers, so finding DL award availability for some partner's FF program should mean that there's low DL award space. [The converse is not true.]

KVS should also show DL award space.

For upgrades, upgrades on partner metal for DL FFers tend to require low award space on the partner carrier, so again one could search for this if the flight isn't DL operated.