My town has built several "transition" apartment buildings for the homeless to give them a "stable" place to live while they in theory get their lives together. They quickly became shitholes, residents destroyed the apartments and especially the common areas/hallways/elevators. They also let any number of acquaintances into the buildings and the apartments, further contributing to the destruction. Half the units are uninhabitable as a result.

If they had to pay rent they would at least be filtering for people who have enough stability/responsibility to have some kind of job or income.

"Just give them housing" does not work for people who have no idea how or desire to live in a house.

Living/loitering/begging/shitting on the streets should not be permitted. Institutionalization may be needed if addictions or severe mental health issues are involved. But expectations need to be higher. Sympathy for and tolerance of antisocial behavior have been utter failures.

The thing with a boarding house is it's not targeted specifically at people who are currently homeless. It's just for anyone who wants to save money on housing. Maybe people who just moved to a new city and haven't found a place to live yet, or people who are just starting out and not making much money. It gives them a place to live before they become homeless.

It would also usually have the landlord living there, and they would be invested in the place because it's their source of income, so they aren't going to tolerate people smearing crap all over the walls or tearing out the wiring to sell for drugs or ranting and raving all night long.

Instituions are full of terrible abuse. Freezing to death on the streets is better than institutions - that is how bad instituions end up being in practice.

I don't have a good answer to the problem.