Void Dimensions is a very simple datapack that turns the Nether and End dimensions into completely empty voids. If you want to change the biome they generate, head to Void_Dimensions/data/minecraft/dimension and edit the "biome" property of the 2 JSON files.
Note: Because of how this datapack works (it just forces the dimensions to generate as superflat worlds with no layers), certain mods may be incompatible with it, such as End's Phantasm, or any other mod which tries to completely take over how either the Nether or End dimension is made. However, it will still work with mods/datapacks like Nullscape, as those only change the noise generation of the islands/cave type, rather than forcing the dimension to generate in a specific way.
Currently, it is only written for 1.20.1, however it should work with both older and newer versions as long as the formatting hasn't changed too much.
