In the mission tree of Pantikapaion (Tag: PNK), the mission 'Meltingpot Nationalism' (panti_meltingpot_nationalism) has three completion requirements: Prestige of at least 20, Stability of at least 1, and that the late-game mission requiring the conquest of 'Link up the Coast' (panti_link_up_coastline) is available. However, is seems that the last of these requirements is apparently met on game start, without having completed any missions. As such, you can very quickly complete this later-game mission, triggering an event that flips your greek-cultured provinces to a new culture group.
In the mission tree of Pantikapaion (Tag: PNK), the mission 'Meltingpot Nationalism' (panti_meltingpot_nationalism) has three completion requirements: Prestige of at least 20, Stability of at least 1, and that the late-game mission requiring the conquest of 'Link up the Coast' (panti_link_up_coastline) is available. However, is seems that the last of these requirements is apparently met on game start, without having completed any missions. As such, you can very quickly complete this later-game mission, triggering an event that flips your greek-cultured provinces to a new culture group.