Stack Trace:
java.lang.IllegalArgumentException: Unable to find a field that matches {modifiers=[required: 10000, banned: 1000], type={ type input instanceof interface java.util.Map }}
at protocollib.jar//com.comphenix.protocol.reflect.FuzzyReflection.getField(FuzzyReflection.java:352)
at protocollib.jar//com.comphenix.protocol.injector.packet.PacketRegistry.createNewRegister(PacketRegistry.java:168)
at protocollib.jar//com.comphenix.protocol.injector.packet.PacketRegistry.initialize(PacketRegistry.java:292)
at protocollib.jar//com.comphenix.protocol.injector.packet.PacketRegistry.getClientPacketTypes(PacketRegistry.java:327)
at protocollib.jar//com.comphenix.protocol.injector.PacketFilterManager.(PacketFilterManager.java:120)
at protocollib.jar//com.comphenix.protocol.injector.PacketFilterBuilder.build(PacketFilterBuilder.java:121)
at protocollib.jar//com.comphenix.protocol.ProtocolLib.onLoad(ProtocolLib.java:183)
at io.papermc.paper.plugin.storage.ServerPluginProviderStorage.processProvided(ServerPluginProviderStorage.java:59)
at io.papermc.paper.plugin.storage.ServerPluginProviderStorage.processProvided(ServerPluginProviderStorage.java:18)
at io.papermc.paper.plugin.storage.SimpleProviderStorage.enter(SimpleProviderStorage.java:39)
at io.papermc.paper.plugin.entrypoint.LaunchEntryPointHandler.enter(LaunchEntryPointHandler.java:36)
at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:510)
at net.minecraft.server.dedicated.DedicatedServer.initServer(DedicatedServer.java:286)
at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1136)
at net.minecraft.server.MinecraftServer.lambda$spin$0(MinecraftServer.java:323)
at java.base/java.lang.Thread.run(Thread.java:1583)
Dump:
Parameters:
[NULL]
Sender:
com.comphenix.protocol.ProtocolLib@b7e8030[
statistics=
packetTask=
tickCounter=0
configExpectedMod=-1
updater=com.comphenix.protocol.updater.SpigotUpdater@33f3ea6d
redirectHandler=
scheduler=com.comphenix.protocol.scheduler.DefaultScheduler@4c739323
commandProtocol=
commandPacket=
commandFilter=
packetLogging=
skipDisable=false
isEnabled=false
loader=io.papermc.paper.plugin.manager.DummyBukkitPluginLoader@13657bf9
server=CraftServer{serverName=Paper,serverVersion=1.20.6-130-5d8e53d,minecraftVersion=1.20.6}
file=plugins/.paper-remapped/protocollib.jar
description=org.bukkit.plugin.PluginDescriptionFile@5eddd7cc
pluginMeta=org.bukkit.plugin.PluginDescriptionFile@5eddd7cc
dataFolder=plugins/ProtocolLib
classLoader=PluginClassLoader{plugin=ProtocolLib v5.1.0, pluginEnabled=false, url=plugins/.paper-remapped/protocollib.jar}
naggable=true
newConfig=YamlConfiguration[path='', root='YamlConfiguration']
configFile=plugins/ProtocolLib/config.yml
logger=com.destroystokyo.paper.utils.PaperPluginLogger@5e7b708b
lifecycleEventManager=io.papermc.paper.plugin.lifecycle.event.PaperLifecycleEventManager@465d13ae
allowsLifecycleRegistration=true
]
Version:
ProtocolLib v5.1.0
Java Version:
21
Server:
1.20.6-130-5d8e53d (MC: 1.20.6)

This is fixed in the latest dev builds. Find them here: https://ci.dmulloy2.net/job/ProtocolLib/