I have friends living in Lisbon and Porto for 10+ years, others that were born and raised there. All of them mention how entire neighbourhoods are slowly being emptied out from locals and getting rented on AirBnB. It's more profitable to rent an apartment short-term for a season than having permanent tenants. There are neighbourhoods hollowed out from people living in them and are just boxes to be rented during peak tourism season and left empty during winter.
It's not so nuanced if you see the transformation happening in your city, you notice your friends living further and further away from where they grew up, you walk through the same places and see the language being spoken on the streets is not what you were used to. You check prices for T1 and T2 apartments and they skyrocketed, are very hard to find through real estate services but can be found easily on AirBnB.