They can't mark and track these with GPS? It seems like it would be a smart idea to keep notes on the precise location of every mine, and whether or not it's been removed or exploded. It's not like it's the 1950s, when a landmine's location was a mystery after it was buried. (Or is Russia planting these mines?)
Tbf Russia's PFM-1 is based off the US' BLU-43. The difference is the US went "Oh wow, this is a really bad situation" and stopped using them half a century ago.
Double tbf: Ukraine also has 5.5 million of these mines themselves.
The vast majority are from Russia and the ones Ukraine uses are mostly anti tank mines which are less dangerous to individuals while Russia is using a shit ton of anti personnel mines.
Putting antennas and batteries in mines increases production cost.
The mine would broadcast it's signal, effectively telling the opposing army exactly where it is so they can disarm it. Effectively rendering mines useless, more of a speed bump than anything.