I don't think this is so farfetched as some might believe.
But Austria and Russia had been moving into the Ottoman territories for years. Only Prussia stopped Istanbul from being conquered by one or both by 1790 timeline.
France, nominally allied to Austria by marriage, had unusually good relations with Austria at this time and Britain was plainly busy.
I suspect France would not have attacked Anatolia but perhaps an early invasion of Algeria and/or Egypt.
The Ottoman was a rotting corpse propped up by Europeans whom didn't want a real rival seizing it.
In many of my timelines, I have Prussia being ripped apart in the 7 Years War, leaving Austria and Russia to tear up the Caucusus, liberate Rumelia (Ottoman Europe excluding Greece) and Greece, reconquer and rechristen Constantinople, as Egypt declares independence and conquers Syria, Persia overruns Mesopotamia while France and Spain attack Morocco and Algiers.