All Januar IBANs support receiving EUR payins. The DK IBAN also support receiving DKK payins.
If EUR is sent to the DK IBAN it remains in EUR on the EUR account.
If DKK is sent to the DK IBAN it remains in DKK on the DKK account.
Hence, the DK IBAN can be used to receive both EUR and DKK, while the DE IBAN and LU IBAN only support EUR payins. Any payins with an unsupported currency will automatically be converted to EUR.
More info available on:
Which currencies are currently supported?
Which countries can I send to and receive payments from?
IBANS with supported currencies and payment schemes
Where can I FX exchange one currency into another and during which hours?