> part of the problem of the war on drugs, many methods of harm mitigation and recovery are barred from users

That is a problem for the US, sure. Australia, where I live, has supervised shooting galleries and more of an addiction as health issue approach.

That said, if you had a chance to look at the US graphs linked above - there was a plateau period of high deaths in the US of some three and half years showing no much evidence of users learning to "safely handle and dose fentanyl" followed by a sharp decrease in deaths that corresponds more with a change in policy than an increase in user knowledge.

I would suggest this may be a somewhat more complex and multivariate issue than your initial upthread postulate acknowledges.