I would never put a drug ordered off the internet into my body. Pure lab grade LSD which has been tested in an NMR — I probably would. I only have one body and I wouldn’t entrust it to random people on the internet.
I think you could estimate the risk in micromorts from taking LSD from darkweb and find it’s not that different from other activities you do regularly (~multiple times a year, if not more)
You cannot estimate the risk of taking internet LSD, that is the problem.
There is also a history of cutting drugs with other substances to give them a unique effect which brings back return customers (i.e. cutting heroin with fentanyl).
And then there is the possibility that whoever produced the LSD screwed up and/or the end product is not pure.