Which are the other cities? These two cities seem to be really high in Pieter Levels' small kingdom. But most of the housing problems in europe at least are caused by golden visas and Airbnbs. Nomads are a tiny amount in comparison
We have no stats on how many of those actually live in Portugal, but it should be noted that the Golden Visa holders only have to visit Portugal for one week per year and that counts towards the five years for citizenship. This was a major draw of that visa.
Not to mention, nomads are cheap people, most of them are traveling to lower cost places where they can avoid taxes.