Any restaurant recommendations for vegetarian friendly restaurants in Siena and Lucca?
Nothing specific but just encouragement--I have never not been able to order a vegetarian dish anywhere in Italy. It definitely helps to practice some basic phrases and know what is in season. If you are strict about things like rennet in cheese, of course it may be more difficult. In that case, I would consult Happy Cow website.
I'll agree it's pretty easy to get vegetarian food in Italy. On my last trip, last Fall, it was tougher to get vegan.
In Siena, the Best of Italy tour I was on stayed at Hotel Chiusarelli and I got a wonderful meal around the corner at Il Masagalano Ristorante Pizzaria. I had ribollita which is a bread soup and this one had beans as well. Sometimes it also has Tuscan kale. It was not on the printed menu but was on the chalkboard. This may or may not be convenient for where you are staying, though! Years ago I also got a good ribollita at one of the restaurants on the main piazza where they run the Palio so I would not hesitate to eat anywhere that smells good.
It's been well pre-covid since I was in Lucca but you will have no problem there.
I have a few "fall back" dishes as a vegan. For soups, ribollita and Tuscan bean soup are usually very reliable, hearty and good. Pasta is never a problem for a vegetarian meal.
The Happy Cow suggestion is excellent although truly in Italy, no problem. I will say that I got very tired of having so much eggplant and zucchini. At the end of a trip to Italy I'm usually craving broccoli, lol!!
Animal rennet is generally found in Italian cheeses. Ribollita is iffy because of the cheese rind and meat broth which may be in it. It is also only served in the Spring at many restaurants especially if outside of tourist zones. Fresh pasta is made with eggs, although often dried pasta is not. It is difficult to avoid animal products in Italy but can be done. In Tuscany look for contorni (side dishes) such as spinach and other greens, cannellini beans, potatoes, mixed green salads, etc.
Pici pasta is the main pasta found in Siena. It is typically made of just flour and water. You could ask the chef or server is the pasta was made with egg (uovo). You will be able to find vegetarian food in almost any restaurant in Italy.