The USSR had ties with unions and communist parties and leftist terrorists. But I don’t think they ever planned any false flags to help those movements. Like the Italian militants supported by the USSR were doing bombings and killings in response to the mob and fascists who attacked first. I don’t think even westerners have claimed the USSR faked any terrorist threats to bolster their factions. “Whataboutism” is used by liberals to cry about leftists because all they had to do was put up a mirror. Not saying intelligence agencies never lie, but it seemed that spreading propaganda to a diverse country whose minorities suffer was sufficient

But there have been some claims of false flags. For example, a KGB defector claiming that the KGB planted a story about the Vatican knowing about the holocaust and not doing anything about it.