I doubt there’s any private flights over Ukraine too. Military planes generally don’t advertise their location in combat zones

It tracks private flights too. I'm only tangentially familiar (though I have an ADS-B receiver reporting to FR24), but my understanding is that it's not required for private flight now, but more and more aircraft are being retrofitted.

Actually, it's more about airspace:

https://www.aopa.org/go-fly/aircraft-and-ownership/ads-b/whe...

"The FAA requires ADS-B Out capability in the continental United States, in the ADS-B rule airspace designated by FAR 91.225:

Class A, B, and C airspace;

Class E airspace at or above 10,000 feet msl, excluding airspace at and below 2,500 feet agl;

Within 30 nautical miles of a Class B primary airport (the Mode C veil);

Above the ceiling and within the lateral boundaries of Class B or Class C airspace up to 10,000 feet;

Class E airspace over the Gulf of Mexico, at and above 3,000 feet msl, within 12 nm of the U.S. coast."