Planning to go to Italy in late 2021 or spring 2022. Retired so don't have to worry about dates. Tourist season and summer are not considered. April, may, October or November. What do you recommend.
It depends on where you want to go. Italy is large and has a lot of different weather. You could "play" with this website:
This is such a difficult question for it really is impossible to predict. We had days and days of 20+ C degrees in late March / early April followed by a bitterly cold snap and now typical "spring" weather of the right mixed bag. There are dry sunny days, sure, but I'm afraid all too often I've found May to be quite rainy in central Italy. October can be fabulous with warm sunny days and little rain but again in other years slightly wintry. Out of all the months you mention, late April / October possibly the "safest" but really and truly who knows? Pack for every eventuality, and bear in mind that although the countryside can look disappointing, most towns and villages still look lovely even in cloud and drizzle.
Most of my trips, from visits to the northern lakes to Sicily, have been in the late March and early April period, which is just before the heavy tourist season begins. I'd say at least 8 out of 10 days are beautiful, though you may need a light jacket or sweater. Nights can still be quite chilly though.