You can push back against your employer. They are not superior to you in this negotiation, and you are wrong to call it "legalities". Your employer doesn't make the law. I successfully pushed back against a big corporate employer way back in the days when I was just a kid at the lowest rung, and they agreed to pay my salary in hard cash instead of a bank wire. So that could be an answer to your "Now what?".

People may prefer a foreign bank for any and every good reason besides mobile OS nerding, and that's nobody's business. Certainly not your employers business.

As for BankID, I know of it and it might just as well be called ThrallID from how ridiculous and pathetic it is that people would let their IDs be controlled and owned by private banks. You must admit that it's nothing to be proud of.

You can also keep your national bank account for your salary and ThrallID if you want to, and just transfer all your money to a foreign account every time you get your paycheck. That way your money is also a whole lot safer, and you get some better peace of mind.