Here's a sticker at a large Danish supermarket showing it isn't necessarily that simple.

It says local and foreign debit cards are free, but Danish credit cards cost 0.9375% extra and foreign ones 1.75% extra. Maybe the rule only applies in the Eurozone?

https://imgur.com/a/UDnathK

Interesting. So foreign cards have to be accepted at the same price?

I know credit card fees are capped in EU, so this might be a reasonable policy, but if merchants and domestic customers have to eat costs due to foreign card costs via higher prices for everyone, that does not seem fair.

Which is basically the government helping an oligopoly instead of fighting it. Of course, considering how attractive the idea of all transactions being trackable must be to governments this is hardly surprising.

What they can do is offer a rebate if you don't pay by credit card.

Swiss (the airline), for example does that.

But I think that goes with the card fee limit of 0.2-0.3% if I remember correctly.