I get the bellow error message when trying to connect to a singelplayer world or even when creating a new one.
After trial and error I found out it is Voidscape, probably incompatible with other mods.
After removing it works [fine.

Attached also the debug Log.

12:28:02.694 game at net.minecraft.server.network.ServerLoginPacketListenerImpl.m_143699_(ServerLoginPacketListenerImpl.java:138) ~[client-1.18.2-20220404.173914-srg.jar%23428!/:?] {re:mixin,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:connectivity.mixins.json:ServerLoginNetHandlerMixin,pl:mixin:A} 12:28:02.695 game at net.minecraft.server.network.ServerLoginPacketListenerImpl.m_10055_(ServerLoginPacketListenerImpl.java:125) ~[client-1.18.2-20220404.173914-srg.jar%23428!/:?] {re:mixin,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:connectivity.mixins.json:ServerLoginNetHandlerMixin,pl:mixin:A} 12:28:02.695 game at net.minecraft.server.network.ServerLoginPacketListenerImpl.m_10050_(ServerLoginPacketListenerImpl.java:69) ~[client-1.18.2-20220404.173914-srg.jar%23428!/:?] {re:mixin,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:connectivity.mixins.json:ServerLoginNetHandlerMixin,pl:mixin:A} 12:28:02.695 game at net.minecraft.network.Connection.m_129483_(Connection.java:241) ~[client-1.18.2-20220404.173914-srg.jar%23428!/:?] {re:mixin,re:classloading,pl:mixin:APP:lightoverlay-forge.mixins.json:MixinClientConnection,pl:mixin:APP:connectivity.mixins.json:NetworkManagerMixin,pl:mixin:APP:connectivity.mixins.json:ConnectionErrorMixin,pl:mixin:A} 12:28:02.695 game at net.minecraft.server.network.ServerConnectionListener.m_9721_(ServerConnectionListener.java:143) ~[client-1.18.2-20220404.173914-srg.jar%23428!/:?] {re:classloading} 12:28:02.695 game at net.minecraft.server.MinecraftServer.m_5703_(MinecraftServer.java:916) ~[client-1.18.2-20220404.173914-srg.jar%23428!/:?] {re:mixin,pl:accesstransformer:B,re:computing_frames,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:infernal-expansion.mixins.json:common.MixinMinecraftServer,pl:mixin:APP:modernfix-common.mixins.json:perf.dedicated_reload_executor.MinecraftServerMixin,pl:mixin:APP:crafttweaker.mixins.json:common.access.server.AccessMinecraftServer,pl:mixin:APP:fabric-biome-api.mixins.json:modification.MinecraftServerMixin,pl:mixin:APP:compactores.mixins.json:MinecraftServerMixin,pl:mixin:APP:balm.mixins.json:MinecraftServerMixin,pl:mixin:APP:fastload.mixins.json:server.MinecraftServerMixin,pl:mixin:APP:byg.mixins.json:access.MinecraftServerAccess,pl:mixin:APP:byg.mixins.json:server.MixinMinecraftServer,pl:mixin:A} 12:28:02.695 game at net.minecraft.server.MinecraftServer.m_5705_(MinecraftServer.java:842) ~[client-1.18.2-20220404.173914-srg.jar%23428!/:?] {re:mixin,pl:accesstransformer:B,re:computing_frames,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:infernal-expansion.mixins.json:common.MixinMinecraftServer,pl:mixin:APP:modernfix-common.mixins.json:perf.dedicated_reload_executor.MinecraftServerMixin,pl:mixin:APP:crafttweaker.mixins.json:common.access.server.AccessMinecraftServer,pl:mixin:APP:fabric-biome-api.mixins.json:modification.MinecraftServerMixin,pl:mixin:APP:compactores.mixins.json:MinecraftServerMixin,pl:mixin:APP:balm.mixins.json:MinecraftServerMixin,pl:mixin:APP:fastload.mixins.json:server.MinecraftServerMixin,pl:mixin:APP:byg.mixins.json:access.MinecraftServerAccess,pl:mixin:APP:byg.mixins.json:server.MixinMinecraftServer,pl:mixin:A} 12:28:02.695 game at net.minecraft.client.server.IntegratedServer.m_5705_(IntegratedServer.java:84) ~[client-1.18.2-20220404.173914-srg.jar%23428!/:?] {re:mixin,pl:runtimedistcleaner:A,re:computing_frames,pl:runtimedistcleaner:A,re:classloading,pl:mixin:APP:modernfix-common.mixins.json:perf.thread_priorities.IntegratedServerMixin,pl:mixin:APP:blueprint.mixins.json:client.IntegratedServerMixin,pl:mixin:A,pl:runtimedistcleaner:A} 12:28:02.695 game at net.minecraft.server.MinecraftServer.m_130011_(MinecraftServer.java:685) ~[client-1.18.2-20220404.173914-srg.jar%23428!/:?] {re:mixin,pl:accesstransformer:B,re:computing_frames,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:infernal-expansion.mixins.json:common.MixinMinecraftServer,pl:mixin:APP:modernfix-common.mixins.json:perf.dedicated_reload_executor.MinecraftServerMixin,pl:mixin:APP:crafttweaker.mixins.json:common.access.server.AccessMinecraftServer,pl:mixin:APP:fabric-biome-api.mixins.json:modification.MinecraftServerMixin,pl:mixin:APP:compactores.mixins.json:MinecraftServerMixin,pl:mixin:APP:balm.mixins.json:MinecraftServerMixin,pl:mixin:APP:fastload.mixins.json:server.MinecraftServerMixin,pl:mixin:APP:byg.mixins.json:access.MinecraftServerAccess,pl:mixin:APP:byg.mixins.json:server.MixinMinecraftServer,pl:mixin:A} 12:28:02.695 game at net.minecraft.server.MinecraftServer.m_177918_(MinecraftServer.java:261) ~[client-1.18.2-20220404.173914-srg.jar%23428!/:?] {re:mixin,pl:accesstransformer:B,re:computing_frames,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:infernal-expansion.mixins.json:common.MixinMinecraftServer,pl:mixin:APP:modernfix-common.mixins.json:perf.dedicated_reload_executor.MinecraftServerMixin,pl:mixin:APP:crafttweaker.mixins.json:common.access.server.AccessMinecraftServer,pl:mixin:APP:fabric-biome-api.mixins.json:modification.MinecraftServerMixin,pl:mixin:APP:compactores.mixins.json:MinecraftServerMixin,pl:mixin:APP:balm.mixins.json:MinecraftServerMixin,pl:mixin:APP:fastload.mixins.json:server.MinecraftServerMixin,pl:mixin:APP:byg.mixins.json:access.MinecraftServerAccess,pl:mixin:APP:byg.mixins.json:server.MixinMinecraftServer,pl:mixin:A} 12:28:02.695 game at java.lang.Thread.run(Thread.java:833) [?:?] {re:mixin}

debug-1.log

Voidscape is not in that debug.log

Oh must have been the wrong one:
crash-2023-11-18_19.15.13-client.txt
Here is another one I just had while retesting.

And now the error I had before and just now again:
debug-1.log.gz

And this was singleplayer? That is extremely weird, that error usually only appears if you're on a server and theres a version mismatch.

It looks like every single item from the mod isn't being registered for some reason.

Actually a ton of items from other mods aren't being registered either in this log. Something is breaking everything.

Yes its Singleplayer, I tried multiplayer as well. Same message.
Oh really? I haven't had any troubles yet ingame.

A bunch of recipes are broken in the log claiming various items aren't registered.

I'm going to close this though as this particular crash is prevented from happening already in the 1.20 versions. Though even if it doesn't crash anymore things will still be broken. I can't fix issues caused by other mods.

Okay, fair :), I guess its not clearly visible whats the other mod? Would have loved to have it in our pack

Thanks for checking!

also getting this with voidscape and some mod.
It doesnt tell me what, but removing voidscape fixes it entirely

Do you have a specific modpack that you're using that I can take a look at?

For me sadly no, its a custom made.