Aside from subjecting the source tabs to the 'acid test', as it were, you would use some lab testing to verify a purchase such as on the DNMs. EnergyControl if you're in the US, possibly some of the national testing programs if you're in the EU. (EnergyControl was not available when I ran my self-experiment.) Another possibility for quality control is moving to the gray market: the analogue 1P-LSD is available from RC vendors and currently is minimally prosecuted, although it's so chemically similar to LSD that it'll probably happen eventually; to the extent that you trust legal sellers more than illegal ones for purity, 1P-LSD would be an improvement. Or you could do both, why not.

Darknet markets, there's a subreddit for it with good information and a helpful community.

Yea, but what's the likelihood of getting arrested from buying like that?

Around the likelihood that it gets earmarked at the post office and you proceed to fall for a Controlled Delivery.

That's my main concern with LSD microdosing. Especially in Vancouver, where fentanyl is finding its way into pretty much every illicit drug.

Avoiding a drug because of it's scheduled status makes a lot of sense, and because of what it might be cut with, but I am not sure why someone, or how someone would cut LSD with fentanyl given how small I thought the effective dose of LSD is comparatively and how different the effects are.

Without gc/ms you just don't know what's in your tab/liquid/etc. That being said iirc it takes milligrams to OD on fent which means you'd be pretty safe with tabs. Liquid is another story.

[REDACTED] acquired LSD tartrate, made solution w/ everclear, and then diluted it such that one sip is roughly 4-8ug based on volume. That's the only real way to microdose yourself, although you could cut a tab into 20 pieces (depends on the lay but a skilled lay is evenly distributed. An unskilled lay will have massive hotspots and thus one would need to dissolve the tab in a solvent or cut it into n->infty pieces)

Buy a testing kit off of Amazon. You should be doing that always anyway.

.onion