Reaming a brake line end

If this were me, I'd simply drill it to size and then use a countersink to champfer the edges of the hole for burrs.

Another issue "modern days" is that most copper gaskets you come across are too hard, and won't seal

Someone on here talked about (heat) anealling them, and I'm sure someone on here posted a supply source for soft gaskets, but sorry, don't remember who/ where.