Ukrainian drones now spray 2,500° C thermite streams right into Russian trenches
arstechnica.com
arstechnica.com
While I have never combined the activities, I do have some experience both flying drones and using thermite. The video showing a drone pouring a stream of molten metal down onto a line of trees looked straightforward enough that I could easily imagine how it might have been done. Thermite is not a complicated technology!
Not that I think it is necessarily a smart move on the part of Ukraine, since Russia can play this game too.
The Hague Conventions on the other hand limit what weapons can be used. in the 1899 article IV may be violated.