Not my image.

Anyways, the world disappears when the portal is lit, and the tempad portal is completely white with no shading while in use.

iPortalTeam/ImmersivePortalsMod#1019

This is probably because Tempad use its own way of postprocessing https://github.com/Toadstool-Studios/Tempad/blob/1.18/Common/src/main/java/me/codexadrian/tempad/mixin/LevelRendererMixin.java#L20

It can disable the postprocessing when immptl is present FabricLoader.INSTANCE.isModLoaded("imm_ptl_core")

I guess as a fix I'll just use the old way of rendering when imm_ptl_core is present as it would be way too much work to rewrite how it works rn. But I dont really understand what that mod is doing to break this so badly...

Someone reported that this issue still exists in MC 1.19.2 https://discord.com/channels/662271867431682058/671895714527182920/1065620640377352223