Jammer are no different than radar. It send a signal and can be triangulated just like any source of EM waves with the right tool.
Now they mount such ELINT stuff on drones but it would be better if they had a small aircraft with 2 or 3 operators inside since drones are easy fool/jamm/destroy, specially to big drone that carry such stuff.
They have the il-112 that can be equiped with a lot of EW/ELINT packages and turn around the front line and listen to enemy signals.
They have the tu-214R but it's a big aircraft and have only 2 or 3 of them. You don't always need such big plateforme for such mission all the time.
We saw that they need such aircraft pretty much anywhere where there are tensions. IMO some 15 il-112 would be nice to back up the tu-214R which is more expensive to operate.
They could even use a smaller plateforme like the sukhoi s-80.
Small countries would also be interested by like Algeria, India, Vietnam... they can easily sell some 15-20 which is a good number for an ELINT aircraft.