Republicanism was fairly common in a few places during the period you’re asking about. Some that stand out most strongly were the Italian communes, some German city-states, and the Hanseatic League had a Republican character (in a mercantile sense) as well through its overarching management. Many towns also received charters in various countries that provided them with more autonomy and often a republican character that generally meant having a class of burgers/merchants gaining seats on a council and a mayor, often directly answerable to a monarch as in the case of England with many towns like the Cinq Ports. Pisa, Amalfi, Venice, Genoa, and many other communities in Italy had very republican characteristics. I don’t know how to cross-post from other posts but there is a common poster on r/Askhistorians that has always given very thorough and well articulated posts and responses on this very topic, specifically on Italian Communes, u/Alvisefalier. This is an area of great interest to me personally so I know a good deal but u/alvisefalier is extremely knowledgeable on the topic.