I personally prefer Interactive Brokers for long-term European investors. Keeping your costs low is important when investing for the long term and IBKR is a very low-cost broker with a transparent cost structure. It has several banking licenses, also in Europe. Secondly, I would choose DEGIRO. It's an easy-to-use and low-cost platform that falls under the Dutch Investor Protection Scheme. To date, it has won 86 European awards, has ~2 million customers, and it is supported by a banking license via its parent company Flatex.