When I set the world to Void on a test modpack of mine, it just loads in a default world no void world

Unfortunately, it's near impossible for me to fix this error. I don't know why you'd use Terralith in a SkyBlock world, but in the future, the solution is to remove Terralith or to disable the Terralith datapack from the world creation screen.
The problem is that Minecraft datapacks override behaviour of the World Type, which I cannot control.

What mods do you have installed?

What mods do you have installed?

about 500ish mods, would be hard. I was testing with my Custom Land Modpack cause back in the day using Ex Nihilo with a void world you were able to decide if you want it to gen as a Skyblock environment or a Basic World

Ex Deorum adds a world type called "Void World" that should be selected by default when you go to "More Options" in the world creation menu. It is supposed to generate a dirt block with a fully grown oak tree on top. I'm able to reproduce your issue with ATM9, I'll have to figure out which mod is the culprit and fix it on my end.

Which world generation mods are you using?

Which world generation mods are you using?

Currently I have like 400ish mods, and yes Some are World Generation Mods. It would take me awhile to try and go through the whole test pack version to list them all

I can test later today about to go get some sleep

My testing says that Terralith is causing this. Can you see if you can reproduce the issue without Terralith?

@thedarkcolour Confirmed, after removing Terralith it works

I might have a few, I use to help one of the other Ex Nihilo devs when they were making their own version

Because Terralith is a data pack, it looks like this is gonna be a little annoying to patch. I'll figure something out tonight.

Since I'll be working on it today, please let me know if you have any suggestions for the mod.