ADM-160 manages to at least function as a decoy with a <200kg launch weight. There are supposedly other EW packages available for it, though whatever jamming modes it uses must be very low powered.EW requires power and it comes from the turbo fan which is quite tiny and reduces thrust. 500 pounds less warhead becomes 350 after new power equipment is added even assuming the tiny airframe can accommodate it and the cooling needed.Like that article states, a B-21 sized/ranged drone is probably not cost effective, but drones could stage from closer to the target to provide capability at a lower price. UAVs could be launched from forward austere air bases or potentially even rocket launched/parachute recovered (looking at you X-58). You could also potentially have a B-52 "escort" the B-21 carrying air launched UAVs; we've seen experimental UTAP-22s loaded onto F-15 pylons. Something larger and more sophisticated in the AGM-183 size/weight range could be carried four at a time as an attritable asset. Perhaps something smaller and expendable, like an extended range ADM-160, could be carried internally for additional support. Maybe the AGM-158B form factor (or stretched version in the AGM-86/1500kg range) could altered to be stealthy decoy; take away the 500kg warhead and you have a lot more space and weight for fuel and an EW payload. A B-52 could carry eight internally; a dozen more externally if that was the only type carried.