When trying to play with the mod in 1.20.6 the following error will appear in the log, crashing the game also.

java.lang.RuntimeException: Could not execute entrypoint stage 'client' due to errors, provided by 'custom-fog'!
at net.fabricmc.loader.impl.FabricLoaderImpl.lambda$invokeEntrypoints$2(FabricLoaderImpl.java:388)
at net.fabricmc.loader.impl.util.ExceptionUtil.gatherExceptions(ExceptionUtil.java:33)
at net.fabricmc.loader.impl.FabricLoaderImpl.invokeEntrypoints(FabricLoaderImpl.java:386)
at net.fabricmc.loader.impl.game.minecraft.Hooks.startClient(Hooks.java:53)
at net.minecraft.class_310.(class_310.java:484)
at net.minecraft.client.main.Main.main(Main.java:223)
at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:470)
at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:74)
at net.fabricmc.loader.impl.launch.knot.KnotClient.main(KnotClient.java:23)
Caused by: java.lang.NoClassDefFoundError: net/fabricmc/fabric/api/client/networking/v1/ClientPlayNetworking$PlayChannelHandler
at setadokalo.customfog.CustomFogClient.onInitializeClient(CustomFogClient.java:24)
at net.fabricmc.loader.impl.FabricLoaderImpl.invokeEntrypoints(FabricLoaderImpl.java:384)
... 6 more
Caused by: java.lang.ClassNotFoundException: net.fabricmc.fabric.api.client.networking.v1.ClientPlayNetworking$PlayChannelHandler
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown Source)
at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.loadClass(KnotClassDelegate.java:226)
at net.fabricmc.loader.impl.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:119)
at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
... 8 more