I've only glanced at the technical manual, but I must've missed the part about the tankers. Makes sense and isn't far off from my assumption about generating it at starbases and refueling ships when they're docked.
On-board antimatter generation is possible, but is extremely inefficient, consuming 10 units of deuterium to produce one unit of antimatter, and is generally a last-resort option.
That part I do recall. Which is why I was thinking that, in Voyager's case with it being a more advanced ship, that the efficiency might have possibly improved to the point it was viable as a primary source. Or maybe "stranded 75,000 light years from home" counts as a last resort and why they seem to ration their deuterium supply.
I like this stuff a lot - I think it makes the universe seem a bit grittier and less "magical" - and it's a shame we never really get to see it.
Agreed. Deuterium can be collected from just about anywhere in space (nebulae being the most useful), dilithium is mined, but antimatter is just "there" as far as on-screen explanations go.

I believe the Demon planet was deuterium. Prodigy I did catch on the second watch through (and confirmed in Memory Alpha). I guess my question is most related to if there's anything canonically stated as to where they get antimatter. AFAIK, PRO was the only reference to actually sourcing it. Otherwise it just seems like it's "there".