I've heard of different people getting 'estrogen blockers' (in quotes because I don't really know what they are) from their doctors along with testosterone. I'm curious if there is a safe and legal substance that does such a thing, and if it's an even slightly common practice.

Hmm. I think this is something prescribed mostly to minors before they are able to take T. I don't think T itself needs an estrogen blocker as it basically kills the estrogen.

I'm getting something, not a hormone "blocker" but a cancer medication that causes an overload that which shuts down the ovaries.
lasts 3 months, during which I'll be starting T, so when this med wears off T should have taken over the whole "no estrogen" function.

Only guys I know who have had them are minors, like you mentioned, waiting for parental consent to go on T.
Andrew