Marco bunq only offers IBANs that start with NL if that is what you're asking. Doesn't matter where you live in Europe. According to European legislation, it shouldn't be allowed for any company / institution to not accept foreign IBANs from other SEPA countries (like The Netherlands), so whenever you cannot use your NL IBAN in Spain, the company / institution is breaking the law. However, in real life, there's a difference between being in the right and actually being treated accordingly.
If you really need an ES IBAN, unfortunately bunq doesn't offer it. But here is some more material on the topic of IBAN discrimination and how you might get help:
Authorities in Spain where you can complain about companies breaking the law related to IBAN acceptance: