I've been searching for a way to use rf signal strength for location discovery. I've tried searching the forums and the consensus is that it is not possible
It is not really, and mostly people assume that you can use signal strength as an accurate measure of distance and thus from two such receivers can calculate a location. That can work outdoors in large flat open spaces but not otherwise.
What can be used to estimate direction is a TDOA system which can be as simple as two antennas and a NE555 timer circuit and a radio. These have been used for decades in amateur radio.
The robot in the video has 4 antennas, so perhaps two TDOA systems which would probably allow you to work out direction.
But TDOA systems are not using RSSI...........