If the Ottomans ever managed to seize the Dalmatian hinterland from Venice, there's a good chance that the cities there would form Ragusa-esque analogues. Like Ragusa, their culture was separate from the Croatian littoral (they spoke Dalmatian, a neolatin dialect - by the Ottoman era, it had become heavily influence by the Venetian language), and they were difficult to conquer from the landward side. It's quite possible that Zara (Zadar), Spalatro (Split), Tragura (Trogir) and Sebenico (Sibenik) could enter into a relationship with the Ottomans very similar to that of Ragusa.
Though in order to achieve this, the Turks would have to displace Venetian control, which was entrenched by the time the Venetian-Ottoman Wars began. One way of eliminating this control would be to have an earlier POD in order to have an independent or at least autonomous Dalmatia. Perhaps the Fourth Crusade never sacks Zara (though you'd have to have it move on to Constantinople somehow, otherwise you butterfly away the Ottomans even if the Basileía Rhōmaíōn eventually falls to someone else)? Another potential POD would be if Domald of Sidraga's liberation of Zara in 1204 lasted longer - IOTL, Venice retook the city just a year later, but if Comes (Count) Domald holds out, Venice's position is undermined. However, even that relatively minor change is probably enough to butterfly the Ottomans, even if not the Turks as a people.
Of course, Venice only achieved final control over Dalmatia in 1409, so avoiding this would keep the cities tied to Hungary-Croatia as autonomous communitates, more amenable to tributary-isation at Ottoman hands. That might be the most realistic POD.
TL/DR: The Dalmatian city-states would be good candidates for this WI.