Wow, seems like everyone’s IFF systems need further improvement...
Prayers for the innocents hurt or killed, and for their families.
Civilian aircraft do not carry IFF. ADS-B identifies civilian aircraft, but it can easily be spoofed, and it is likely that Russian air defense systems are not integrated with ADS-B, for that reason and it adds cost and complexity that may be used by an enemy to deceive.
Commercial aircraft should not need GPS to navigate, it is “nice to have”, but not essential. Civilian GPS is easily spoofed, that is sent deceptive signals to pull the victim off course. If it was GPS spoofing, one wonders for what purpose, unless it was Russians expecting Ukrainian Drones navigating via civilian GPS and luring them into an ambush?