https://pastebin.com/uRi2MJKk

This could be because I'm using Quilt, but it looks like something drastic changed.

Thanks for reporting this! However it looks like the cause of this issue is

Caused by: org.spongepowered.asm.mixin.injection.throwables.InjectionError: Critical injection failure: Constant modifier method modifySizeLimitWhenReadingPacket(I)I in imm_ptl.mixins.json:common.networking.MixinClientboundCustomPayloadPacket from mod imm_ptl_core failed injection check, (0/1) succeeded. Scanned 1 target(s). Using refmap imm_ptl_core-refmap.json

which looks like a mixin from imm_ptl_core: Immersive Portals Core 2.2.5?