Destroy 30 Spy Drones.

The Spy Drones will be present in locations throughout the map and unfortunately, their appearance is completely randomized so a guide for where to find them is useless. First, you will want to unlock a perk, 'Spy Drone Tracking' found in the 'Search & Recover' section of the Projects menu, you will need to purchase either 'Storage Container Tracking' OR 'Datapad Tracking' first as well as unlock tier 3 of these projects. It is important that you don't purchase all of the tracking perks, since you will need to use this tracking to find the Spy Drones and the tracking does not differentiate between what it tracks, so the less your trackers is finding, the better.

Now begins the arduous task of finding 30 Spy Drones. There is no easy or fast way to do this, you will simply need to visit each and every location on the map, see if there is a Spy Drone present, destroy it if there is, then move onto the next location and repeat this until you have found 30. There are thought to be only 34 in the game, which combined with their random chance to spawn in any given location means you will likely need to check almost every single location on the map to get 30.

It is strongly recommended that you make a save before entering a location in case the Spy Drone sees you and flies away, the Spy Drone will see you if you look at it directly for a second or so. It is unknown where they go to, if they come back or if they are gone forever when they fly away so to be safe, make a save before entering a location then head in to find them, then if one of them does fly away, just reload your save to spawn outside the same location and try again to destroy it. I found using the Rocket Launcher was the best approach as it destroys them instantly and you only need to hit somewhere near it to cause enough splash damage to destroy it.

A video with what you should be looking for: