Work permits shouldn't be an issue for international players, and certainly not for EU citizens from Croatia before Brexit. I just looked at the statistics. Both the PL (330 non-English players) and Serie A (340) have a very high percentage of foreigners.
While most countries are similarly represented in both leagues with France and Brazil in first and second, and then relatively similar numbers from Netherland (13), Ghana, Nigeria, Senegal (6/7 in both leagues), the numbers vary strongly when it comes to Irish/British and Balkan players.
Scandinavian countries have almost the exact numbers across BL, PL, and Serie A. Denmark is more present in Germany than in the other 2 and England has more than Itlay thanks to Brentford.
There are about 10 British players in Italy (7 from England) versus almost 45 from Ireland and the rest of the UK playing in the PL. And on the other hand, Serie A has 44 players from Balkan countries versus 5 in the PL. Germany has more balkan players than the PL, about 12 I think. While there are 15 in Spain, but that number is relatively high if you consider that la Liga has by far the lowest total of foreign players, only 222 compared to Italy's 340 and England's 330.