I heard a long interview with the author Sam Quinones a while back. He has done a deep dive on the current drug crisis. How the drugs are made, sold, etc. The book is Th.e Least of Us: True Tales of America and Hope in the Time of Fentanyl and Meth
He has an interesting perspective on what we see as the last group of homeless, who essentially can't be housed, despite having beds at shelters and supported apartments available. Their drug use and paranoia prevent them from following any sort of process to get help.
We've seen this locally with folks camping in below freezing weather despite beds being available at shelters. The "housing first" model is failing because the drug use issue is being ignored by the "experts".
https://a.co/d/fuWbNcC