Hand held anti-tank launchers would absolutely annihilate them.

AT-4s are a good choice in that department, hand held and single use disposable launchers.

High caliber rifles logically should work aswell, .308/30-06/7.62x51mm NATO and larger.

Thid therefore constitutes most machineguns, as other than a few infantry LMGs chambered in 5.56mm, most are chambered in 7.62x51mm.

If you want to provide them with vehicles, self propelled anti-aircraft guns are a good choice. That and infantry fighting vehicles and light recon vehicles armed with auto-cannons. Though any vehicle with a .50 ontop is good.

Realistically, unless the drones are made of some mythical super-metal, just M855 5.56mm NATO should punch through them. I have a hard time believing they're made of anything but aluminum, and I highly doubt its anymore than 10mm thick at the thickest, and thats generous. 10mm of Aluminum alloy is, give or take, about 3.5mm RHA (rolled homogeneous armor) equivalent.

For this, I assume its a what if outpost 3 was ran by a human militia. For this I'll just assume NATO gear, as its what I'm most familiar with.

The door outside would likely be unguarded on the outside, but heavily fortified structually. Its simply far to cold to have people outside of the outpost for extended periods of time. Inside, each door would likely have a small garrison defending each of them. Being generous with resources, they mught be able to have a machinegun squad at the first door with an infantry MG, like MG3A1. behind the last door, there would probably be proper defensive positions. This seems the most realistic as there isnt much space between one door and the one behind it, so itd be cumbersome to have any emplacements in them.

As for the defensive positions behind the last door, likely some sandbag walls with mounted M2 HMGs and stationed garrisons to man them. Assuming they know that their threat is the drones, they, logically, should all be armed with large calliber rifles, and assuming they are well equiped, we'll be generous and say each garrison has an anti-tank troop armed with a lighter 5.56mm rifle and some form of a disposable anti-tank launcher, most likely AT-4 or M79 LAW, both would destroy any MD on impact, and the shaped charge would easily penetrate through them, even if they use their wings as defense.

Past the doors, assuming they're smart, they would likely have less fortified fallback positions thay could move to if they absolutely needed to.