What matters is where the headquarters and key employees are. SE can be based anywhere in EU and even then legal entity stuff isn't what matters.
Origin: German, HQ: German, Accounting regime: German, Main stock listing: German, Executive board: 5/6 German
In fact, you can run any form of European legal entity from any country. I.e., I can create an spółka z ograniczoną odpowiedzialnością (sp. z o.o.) in Poland, but run the business in Germany. It would be complicated and stupid, but legal.