Increase the build limit to Y=2031 in all dimensions.

WARNING: Starting with Minecraft 1.21.2 removing the datapack/mod will corrupt your world! You can find a tutorial on how to remove it safely here.

Does this support custom world generation mods/datapacks?

This datapack doesn't change world generation by itself, but custom world generation mods/datapacks may hardcode the world height. A notable example is Tectonic. The mod version of it is not supported, but if you're using the datapack version you go to /data/minecraft/dimension_type/overworld.json inside the Tectonic datapack folder and change "logical_height" and "height" to 2096.

Does this work with existing worlds?

Officially no, but you can follow this tutorial to transfer existing chunks to a world made with this datapack.

What happens to existing worlds if I remove the mod/datapack?

Removing the datapack/mod in 1.17-1.21.1 will make everything above normal build limit disappear, but since 1.21.2 it will corrupt the world, thus the warning at the top.

If you still don't have a server host I recommend BisectHosting. They have 20 server locations, advanced DDoS protection, an user-friendly panel for server management and if you use promo code OBYDUX you get 25% off.