I don't read Portuguese but there's nothing specifically regarding beaches in their courtesy translation [1] beyond avoiding areas next to SAR helicopter bases (which is fair enough) and there's nothing on their UAS restrictions map [2] that would be unusual in any other EU country.
I have flown (below 120m obviously) in Portugal near the beach with a <250g drone after checking their UAS map so it would be good to know what I missed? Possibly you are referring to some additional local restrictions?
1: https://www.anac.pt/vPT/Generico/drones/operacoes_transfront...