Venetia existed within the Exarchate of Ravenna, as part of the Byzantine Empire, and what happened in the Exarchate mattered to Venetia.
An excerpt of the “Liber Pontificalis” for Pope Zachary about Lombard attacks on Ravenna around 742.
An account of the anti-iconoclast rebellion of 726–727 in Byzantine Italy, from the “Historia Langobardorum” by Paul the Deacon.
Venice started as a Byzantine duchy, ruled by a “dux”, but at some point, they started choosing their own dux — or doge. When, or even who, is not clear.
Jacopo TIepolo, doge 1229–1249, left an impact on Venice, which is still clearly visible today.