Does anyone know if there are ferries from Iceland (any harbour) to Portugal or Spain?
The only company I know of that runs regular ferries to Iceland from either Denmark or the Faroe Islands is Smyril Line. Also, I'm Portuguese and have already been to Iceland and I can tell you I've never heard of a commercial ferry company doing that route.
I also found a website with all the ferries within Iceland, not sure if it is of any value to you: https://www.rent.is/blog/ferries-in-iceland/.
There are no scheduled connections.
According to ferrylines.com, connections from Iceland go to the Faroe Islands and Denmark, only.