There are many historical examples proving that false flag military operations in themselves is not a conspiracy theory, it's something that has happened and will continue to happen.
What is extremely important though is context. A famous false flag operation from history, for example, is the "Gleiwitz incident": Nazi Germany attacked its own radio station in 1939 to justify attacking Poland.
Even at the time, it was obvious that something about this was fishy, because anyone could understand that Poland did not have anything to gain by starting a war with Germany -- a Germany that by the way had annexed Austria and the Sudetenland the year before.
Of course, nobody in the German political leadership actually cared what people believed, much like Russia today spreads misinformation about Ukraine that is borderline laughable. It's not always about the information being believable, it can also be a show of force: I'm lying to your face, we both know it, but what are you going to do about it?
That does not imply that it is not a conspiracy theory. It implies that it is a correct conspiracy theory.
"Ukraine bombing its own cities to make Russia “look bad” is such a claim. "
Individual false flag military operations are not uncommon, but widespread destruction of one's own country for propaganda purposes would be extraordinary.