The EU-wide rules apply in Portugal the same way they apply everywhere else — those are on the rules page. This page carries its producer register.
Where businesses register
Portugal keeps its list of packaging businesses in Registo de Produtores de Produtos, run by the Portuguese Environment Agency (APA). The rules call this a producer register. Being on it is what allows packaging to be made available in Portugal at all, so it is usually the first thing a business shipping there deals with.