Publicly paid for rent free housing. Not group shelters. Full on housing. That's literally all it's ever taken. Season on some free mental and medical Healthcare and you've got a recovery sandwich. Even if they don't end up fixing their lives, the amount it costs the public to just give them this is cheaper than it costs to have the police harass them, build anti-homeless infrastructure, and repair damages caused by the unhoused from defecation or public property damages. The other one-two punch is fixing economic problems, which rent caps, unions, minimum wage being a living wage tied to inflation,, and changing fines to imprisonment for corporations doing crimes will fix a lot of that.

It's too bad this can't happen while corporations can buy the government with "donations" and lobbying (legalized bribery), and massively benefit from homelessness as a way to force people into exploitative work, or imprisonment for cheap legal slave labor (See 13th amendment). Only way I can think to fix that problem is to remove the source of their power, which is to pull money out of the equation. Essentially building communities that work together without money like we used to, though the government has standing orders to kill or break up people who try that (see Malcolm X, M.L.K. Jr., or places like lake Lanier).