Finland has essentially zero homelessness, yet they have drugs and mental illnesses. The U.S. has nearly 10x the rate of homelessness as Canada, yet they both have drugs and mental illnesses. The differentiators are availability of affordable housing and supports to make that housing work for those with highest needs.

This is very true and a good starting point for a tip. I'll note that you have presented a US specific option on a global site, but that said, many other countries will have similar options available like a rent bank or utilities arrears assistance, worth looking into.

However, as many are already pointing out, the challenge in most communities at this time is that these supports are vastly over-extended. Apart from a few outlier countries like Finland which is still building new social housing, the number of people in housing need is increasing faster than affordable options, and therefore homelessness is rising.

I've worked in the sector, people experiencing homelessness are kept well informed on available supports. Unfortunately they are vastly under-resourced. For example our community has a rent bank but it always runs out, which isn't an issue of awareness.

This is very much incorrect. Programs such as Housing First and permanent supportive housing have demonstrated that virtually no single person is "unhouseable". Rather, they just need the right housing and right supports to keep them in that housing. Mental illness and criminality are not the problems, sufficient housing and supports for those living with mental illnesses and who have criminal histories is the problem.

They aren't designed to be ineffective, they are so deeply under-resourced that they: 1) Lack sufficient staff to keep pace with need, and 2) Have added a number of criteria so they can prioritize resources to those with greatest needs. You can't design your way out of that kind of mess, the only improvement would come from more funding to support organizations.