Two straightforward treatments I’d want to see tested:
1. A significant “hotel tax” or “vacancy tax” to make it very expensive to let housing sit idle. Reduce the profitability of tourist rental and units will shift back to local rent.
2. Significantly expand the supply of housing by removing barriers to development. This phenomenon is happening around the world as cities try to keep existing neighborhoods under glass and prevent any change, damning younger generations to have no place to live.
Another thing I would love to see is the development of new cities with robust transit connection to the nearby older ones. I don’t know enough about Dublin to be specific, but I do know that across the US one of the things that is happening is a generational trend toward wanting urban living, to the point that many people don’t even consider living in suburban or rural towns. However there’s no reason we can’t build new “urban” cities: places starting with a Main Street, compact walkable design, street grid, designed to organically scale up to a genuine large urban center over time. This was common practice in the 1800s, and we have plenty of models around the world to copy from, we just quit doing this in the car age. Why not bring this back?