Game crashes after a couple of minutes after entering the portal. Playing singleplayer.
Playing the "Better Minecraft Plus" modpack. version 22
Crash report is large so here's it's pastebin: https://pastebin.com/cvrCM2Mj

Could be caused by a lot of things, and does not necessarily have anything to do with Atum.
Try removing the mod Performant. Tends to cause more issues, than it fixes.