It's more than Denmark, the Nordics in general use digital signatures for accessing banking, government services (tax agencies, healthcare, pension systems, etc.), online payment ID checks, and so on.

In Denmark I believe NemID/MitID is the most used one, here in Sweden we have BankID (most used), and Freja eID, there are a few smaller ones as well; Norway has their own BankID that is independent from the Swedish one; Finland has their own as well (and I heard it's been live before the 2000s).