This is a long documentary so I am sure there are better videos that get right to the point but this street is one of the more famous examples in America that you will hear brought up repeatedly in places like reddit.

https://www.youtube.com/watch?v=DXyXYJg9SyY

You get a good sense at 21:00 in the video.

It's when people who don't have a house to live in gather to do drugs.

When people who do have a house to live in gather to do drugs, we call it the suburbs.

"Open drug scenes are gatherings of drug users who publicly consume and deal drugs."

I hadn't heard it either, and the PDF didn't load for me.

it's defined in the paper but of course that's behind a paywall. Considering how many times the OP used the term, it would have been helpful for it to be defined.

Here is the full paper: https://sci-hub.se/10.1159/000259053

It’s the new “you’re siding with the terrorists”