At that price point, I would be looking for pre-owned iPhones. Why iphone? Because they keep updating their software longer than any other manufacturer.

A used phone. New budget phones are generally pretty bad, so I would recommend something like a Pixel 6/6a or a Galaxy S20/S21.

The strongest OPPO you can find in your neighborhood.

€250 is a hard price point but a Samsung A series is probably going to give the best performance for the money.

My vote goes to the Realme 10 or one of the Motorola Edge. Both are really solid choices.