Today's message from the Points Guy has some useful information about EU Rule 261. Here's a quote:
"The European Union’s generous passenger compensation rules just got even more generous.
The 27-nation bloc’s top court on Tuesday ruled that compensation is now due when a flight departs more than an hour earlier than originally scheduled. When that happens within 14 days of departure, the flight is considered canceled under those rules, known as EU261."
And here's the link to the full and detailed article: https://thepointsguy.com/news/eu261-early-flights-compensation/
Note that "...the rules apply to flights that are within the EU or departing the EU — not flights that arrive into the EU from outside of the bloc."