Probably the case of since the Ottomans are in the Modern Age, they needed to have a more modern looking ship, unfortunately.
The Xebec look is already given to the generic Corsair unit.
https://civilization.fandom.com/wiki/Corsair_(Civ7)
This can be either Xebec or Caravela Latina. Both of which are fast ships. (Though the latter is very small, only 20 meters long and 6 meters wide at maximum (Except Portuguese Caravela Redonda which were slightly bigger))
Some early xebecs were oared similiar to any Mediterranean Galleys (and notoriously known to use galley slaves, practices common in the Early Modern Period (1500-1700 or 1800 AD) but not before. As they were pirates (or Ottoman Privateers), captives earned from each raid are (un) conveniently assigned to rowing benches. But some did not.
Firaxis rarely got its right when comes to the 17th-19th Century Navy, in previous games there were Frigates, now Ships of the Line. and both were--in their minds--interchangeables.
In truth they were made for different tactical roles. Ships of the Line was made for 'Line of Battle' tactics--required to carry more, and bigger guns AND also required to be built strong, not just to witstand the merciless seas, but more importantly, enemy broadside salvoe, this inevitably reduced the ship's speed and manuerability (some were even ill built, packed with more guns than those actually useful (Three or even Four decks)), and not really manourevable. These were Spanish Flagship (can't remember a name, but Horatio Nelson won this at Trafalgar with a cost of so many Royal Navy crew, and his own life), and USS Pennsylvania.
The other tactical (and also strategic) needs are speed, and Frigates (as well as Sloops, Brigantines, and Corvettes) were built for this matter. Just enough guns to do an average fight (usually against either pirates or enemy naval patrol) or to be naval raider themselves. Frigates were fast, but armed with less cannons (and those were middle weight guns like 12 or 24 pounder mounted (usually) a single continious gun deck (double decked frigates were also existed, categorized as 'frigates'. but these were not common). These were made to be fast and thus strenght emphasis was only just to be seaworthy. (though some 'Frigates' were really though, such as USS Constitution. Intentionally ordered by The Congress to be nearly as tough as British Ships of the Line, but equipped as Frigates. Brits called these 'Heavy Frigates').
Basically it can be remodelled with broadside cannon, and also to be long and more slender.
Think of Civ6 iterations.