In Italy, for regional trains, since 2025 Trenitalia gives the reimboursement automatically to your credit card if you purchased the ticket electronically. [1]
Good news I guess? I was in this situation in 2024 and asked a fellow traveler who was Italian what recourse we had. He laughed and replied “none, we’re fucked”.
Meanwhile I had a terrible experience with DB (Deutsche Bahn) during the European summer two years ago, although it was partly out of their control (weather related delays and cancellations), I had to take awful detours, had paid for 1st class on ICE and ended up on regional trains up and down and lost one day of my holidays. No compensation whatsoever, although maybe I had to fill some online form for that.
I was positively surprised at their proactive communication. The money was on my account within the week!