Yes, it could be coming from the seal of the rear hood to the engine. Do I think it is? Not likely. I agree, a good source is the ac drain. It won't be happening if the ac isn't on. I also think it could be the heater core. These things don't last forever.
I'd pull the carpet on that side, so you don't create a rust problem and create more damage. Put a rubber mat down and use the vehicle and start investigating and documenting when it is happening. Oh, and keep the water/ antifreeze sopped up.
Or give it to a reliable dealership and let them spend your money doing the investigation.
Ric and Jan Golding
2016 Jayco Seneca 37FS
2016 Chevrolet Traverse
2018 Cheverolet Silverado