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I ate an acorn once. It was fucking rank.

Acorns aren’t edible unless processed. Nixtamalization is how indigenous tribes in the Americas made ground acorns into an edible meal. Presumably one could boil nixtamalised acorns and derive a brew, but I’ve never heard of it being done.

Ray Mears and his mate Gordon, (who is most definitely not a moron), processed acorns into an edible meal years ago.
Shelled, roughly broken up, into a net, into a stream to allow the fresh water to wash away most of the tannins,
then slowly roasted, at the lowest heat possible from a fire,
then ground up and made into a paste/dough,
formed into rough flat breads and cooked over the fire on a griddle.

There are rumoured to be groves of Oaks in Italy,
from a very local sub-species that gives rise to tannin-deficient acorns that
are edible without all that above.

Edited to add link to Ray & Gordon making acorns edible
https://m.youtube.com/watch?v=w0hlZIxqSaY