Harm reduction was originally defined as reducing the impacts of policy/war on drugs (health and legal consequences) for people who use drugs. But you rarely see governments or health authorities use this definition. The focus on prohibition and policy is usually absent. Instead, harm reduction became about reducing the harms of drug use, which focusing on individual behavior, and not the policy and law that makes using drugs so much more dangerous then it ever needed to be.
That's a bad thing, it helps governments avoid looking at their own failed policies, and continues blaming the person and not the policy. It's a cooptation of a concept that was intentionally critical of the drug war.
#SafeSupply means legal versions of currently illicit drugs. It means moving beyond the drug war and beyond harm reduction. An illegal #SafeSupply cannot exist. Even if it's a known source that does not mean it's a #SafeSupply, if it's illegal, there's nothing safe about it, the justice system makes sure of that. Only harm reduction is possible under Drug War laws, not #SafeSupply.
If you're buying diverted prescription pills, even if your risk of overdose is greatly reduced, the threat of enforcement still follows, so it's not really safe supply, just good harm reduction.
That's why breaking down the barriers that prevent access to legal drugs is a priority. Same with making safesupply programs that can compete with the illicit market in ease of access.