>How do people magically get their hands on these various substances
Some people sell psychedelics in person. In my country they're incredibly rare and I've never seen anyone sell anything except mushrooms or LSD. So the fallback is the darknet.
>and know that they’re authentic?
If you're buying from the darknet, user reviews. Other people make good guinnea pigs. Otherwise, there are reagents you can use to test to make sure you've got DMT. But generally people just smoke it and see what happens. DMT is very unique, if the substance you have is something else it will be noticeable very quickly.
Some people sell psychedelics in person. In my country they're incredibly rare and I've never seen anyone sell anything except mushrooms or LSD. So the fallback is the darknet.
>and know that they’re authentic?
If you're buying from the darknet, user reviews. Other people make good guinnea pigs. Otherwise, there are reagents you can use to test to make sure you've got DMT. But generally people just smoke it and see what happens. DMT is very unique, if the substance you have is something else it will be noticeable very quickly.