One hope with all those mines is that thermal imaging has become cheap and because of thermal lag due to the difference in the ability of the mines and surrounding dirt to heat and cool, one can much more easily spot the mines in bulk rather than the tedious process of using metal detectors or mine sniffing dogs or rats. This detection should apply to majority plastic mines as they will insulate the soil above them allowing the soil to heat and cool more rapidly, while metal mines will act to delay heating and cooling. A commercial use of this has been looking for places where asphalt overlays have become debonded from concrete structures such as in the paving on top of bridges as well as finding cracks and voids.
Ground penetrating radar has also become cheap, but it requires closer proximity to the mines and, because it is using a far longer wavelength, is less able to tell the exact shape of the item, though it can see much deeper into the soil.
Also a big help is cheap computation ability - farmers can up-armor tractors with plows and let them run remotely or semi-autonomously to dig up whatever metal might be out in the fields with little risk to people.
The big question is for booby traps left in residential and industrial areas where none of these are particularly effective. Russian troops are already at low morale and they seem more angry at their commanders than at Ukraine and I hope that it makes for a general inclination to either disobey an order to booby trap or to make them ineffective or obvious.
Were I to press hard on this war I'd be looking at dropping as much fentanyl onto Russian positions and behind their front lines as I could. It's not as if the US doesn't intercept enough to do the job, might as well put it to a better use. Foil packets with a dozen pills each, dropped from drones. Addiction or overdose; don't care at this point. The Russians can pick up some going forward or retreating. For extra points use degradable plastic to expose the pills to the environment in a 3-6 month period out in the open.