this should explain how the end portals in the stronghold got there in the 1st place
well i made a recipe it is just as hard (possibly harder) to make the end portal with this recipe and it is very rewarding when you make it. You get to have it in your base
Warning once you place the end portal frame you cant break it since it is an industrictable block so be very crareful where you place it
wanna know the recipe here it is
E= Ender Pearl
O=Obsidian
E E
O O
OOO
here is a super cool datapack: https://www.planetminecraft.com/data-pack/cave-biomes/