https://pastebin.com/zHuzvt9M

Minecraft version: 1.16.5.
Ars Nouveau version: 1.25.10
Gecko Lib version: 3.0.106

Upon creating a world, everything crashes.
I've deleted several mods in the course of trying to resolce it, but I can't seem to make it work.
I've deleted Optifine, as suggested on the Discord Server, and several other potentially conflicting mods,
So far, nothing seems to resolve the crashing.
I've looked through open and closed issue reports here on GitHub, hoping to find answers.
However, even after trying to downgrade both Ars and Gecko which presumably was a solution to a similar issue, the crash still persists.
I'm posting this report here so that the issue doesn't get lost on the Discord Server.

I hope your day is going well.

Found the culprit.
Apparently it had something to do with a datapack I was using, which removed overworld dungeon, mineshafts, lava lakes and caves upon world generation.
Not sure what exactly from the datapack conflicted with Ars Nouveau, but it had to do with the datapack's contents.
Removing the datapack entirely resolved the issue.

If anyone ever experiences a similar error and crash, look at your datapacks too.

Cheers!