I'm in the process of rebuilding my modpack on 1.21.1, and this time tried to add Immersive Portals.

After configuring the dimension stack, i tried to create a new world in Creative, but when i pressed "Create" button it disconnected me, like the internal server gave up immediately.

Here's the Gist with the latest.log showing the problem.

PS.: I also removed the Iris/Sodium lock because i currently with Sodium 0.6.0 beta 4