Seaports that are ice-free year-round.
Nah, that is 19th century thinking.
Murmansk is ice free year round. So is Sochi. St Petersburg can have ice, but it’s rare and that’s why God created ice breakers.
In fact, ice breakers are what rendered 19th century norms dissolved. They just don’t have this problem anymore.
They also have Novorossiysk on the Black Sea.
There just is no maritime constraint of consequence since icebreakers arrived in society. Europe has nothing they don’t already have — other than Muslim immigration.