Sicily

Lots of places have "constant" earthquakes. Most of them are small enought to barely notice if you notice them at all.
An earthquake large enought to cause travel issues is pretty unlikely. Etna eruptions are a bit more likely, but even that is not likely to impact your trip.
I loved the RS Sicily tour.

I think constant earthquakes on Sicily are on a par with constant earthquakes in California. The vast majority are non-events; once in a while a big one hits and then it's news. But nobody knows what's going to happen in 2027.

We did a two-week tour on Sicily in 2024 (with OAT, it was great). I was unaware of any earthquakes whatsoever. The only time earthquakes were on our radar at all was in Ragusa, where we learned that it and many other towns in that region were totally destroyed by an earthquake in 1693.

As mentioned, you are more likely to be affected by ash from Etna, particularly if you plan to fly in or out of Catania. Palermo is a safer bet, or the train, which acrosses the Messina strait on a ferry! Here's a thread from a forum member who was recently affected by "Mama Etna" spouting off: https://community.ricksteves.com/travel-forum/trip-reports/mama-etna-is-angry-and-i-get-a-longer-trip

If you’re concerned about the possibility of a natural disaster a year from now and being stuck someplace, you probably shouldn’t travel far.

If you are flexible, you will never be stuck. Worst case, Etna erupts, ash shuts down Catania Airport for a day, a few, a week.

If it happens while there, there are lots of places on the island not affected, even 20 miles away.

If it happens while trying to fly out of Catania, then you have choices. Maybe find a spot and chill for a few more days. Maybe get a flight out of Palermo. Maybe take the train to Naples, or a ferry. Maybe train or flight to Rome to get a flight out.

Personally, I wouldn't mind being around during an eruption, probably a highlight of the trip.

Echoing Paul, my only caveat would be to NOT plan to fly out of Catania to connect to a transatlantic flight. Either plan to fly out of Palermo, plan to leave by sea, or plan to spend time on the mainland, so you have only minor rescheduling difficulties if Etna acts up - as it unpredictably and too frequently does.

Please do not skip Sicily. It is wonderful.

Agree with others: don't skip Sicily due to Etna concerns!
DO build in flexibility in your schedule should a problem arise, and buy travel insurance.
I have clients going in May 2027 and will be alert to potential impacts then, with backup plans ready to go!

I wouldn't worry one bit about earthquakes impacting my vacation. I wouldn't waste money on trip insurance because of a fear of earthquakes.

An Etna eruption has more chance of cancelling flights in and out of CTA but even that is not a normal event and there's multiple other ways to get off Sicily to your connecting airport home. You could fly out of PMO or take a ferry for less money than your trip insurance would cost, and you'd have 0% hassle dealing with an insurance company trying to screw you.