Comment by kragen

And software. The Ukrainian drones largely run on the open-source Ardupilot.

GPS is fairly easy to jam, and despite the purported end of Selective Availability, unencrypted GPS can be turned off entirely without affecting US military GPS. Cruise missiles have been using terrain models for decades now, since well before GPS (a major reason high-resolution DTED used to be classified) which just requires a computationally cheap particle filter and appropriate sensors. We can expect belligerents in upcoming conflicts to maintain strategic stockpiles of the relevant electronics, which are more compact than even cocaine or fentanyl and therefore difficult to blockade.