As we can see, the military ADS-B adoption rate varies between around 10% in Israel to 90% in Saudi Arabia.
The same, a bit more detailed, for some selected countries:
Here, you see the share of aircraft which use Mode S only or additional comms, ACAS, ADS-B, or all three.
Finally, we know that military aircraft can switch off ADS-B when they choose to. This happens regularly, some only really seem to use it en-route in “safe” airspaces but switch it off for their approach to make it ever so slightly harder to see where they land (well, not really but that’s another story). But for that, and other information such as ADS-B equipage per aircraft type, you’ll have to read the full paper.
 Matthias Schäfer, Martin Strohmeier, Matthew Smith, Markus Fuchs, Vincent Lenders, Marc Liechti and Ivan Martinovic. OpenSky Report 2017: Mode S and ADS-B Usage of Military and other State Aircraft. In IEEE/AIAA 36th Digital Avionics Systems Conference. September 2017.
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