We will be in Florence for 2-3 days in early July. I want to take my family to the duomo, but don’t want waste time in line, and I don’t want a paid tour. When is the best time for shorter lines?
I would guess well before the opening time but hopefully someone else has some more insight.
I would try well before opening time, too.
Be aware that most churches are closed to tourists on Sunday mornings because of Mass.
Note that the Duomo opens for visitors at 10.00. 09.30 might be a good time to get there.