Today, when I was looking for SHD tech, I entered an underground tunnel. I collected 5 Hyenas Keys in the tunnel.
The Division 2 Hyenas Key Location, Lets Explain Where They Can Be Found
You can find the Hyenas Key in the small cabinets placed on the walls of this tunnel.
You will find the underground entrance of this tunnel in the West Potomac Park area, which is located on the bottom left side of the White House.
You can reach the underground entrance from the place where my character stood on the map I gave in the image.
Also, I found two True Sons Keys in this underground tunnel. These keys are also useful for opening some boxes in The Division 2.