Depleted uranium is far less radioactive than natural uranium, one of it's uses is in fact as radiation shielding....

That being said, uranium in and of itself is toxic to humans.

Depleted uranium, DU, is used in projectiles due to it's ability to punch through armor, and funny enough, it is also used as armor plating in some tanks.

As a projectile DU has the advantage of being self sharpening and flammable, so if I understand it correctly, when a DU projectile hits an armor plate the energy of the impact causes the DU to self sharpen, increasing the armor penetration capabilities of the projectile, and once it has penetrated, the DU projectile has broken up into many small sharp needles and the added heat of that transformation causes it to catch on fire.

I really doubt that Russia is using DU as a direct ammunition in their drones, it seems more resonable to think that the use of DU is to balance the drone, due to the high density of the material it would take up little space in the drone.