Q&A for How to Obtain String in Minecraft

Villagers will sometime trade for string. Witches have a chance to drop string upon death. Steal string from other players. Use Creative Mode/Commands.

You can use a map and just explore the world, make sure to bring a map if it gets dark and you don’t want to fight monsters. Also bring lots of nutritious food (bread, cooked meat) and make sure to light dark places up! Don’t get lost.

Mob loot must be disabled. Go to world settings and click on "Entities Drop Loot" to turn it back on and the mobs should drop stuff. If they still don't drop anything, it is a bug and you can report it on bugs.mojang.com.

Trade with Piglins with gold, make sure to have the armour with you. Or loot fortresses in the Nether, with bricks and looking red. That's how you can get it.