I found a packet error with 1.20.5, I saw that the com.comphenix.protocol.wrappers.WrappedLevelChunkData$ChunkData class cannot be initialized because the constructor for the real packet changed.
On 1.20.4 it was
public ClientboundLevelChunkPacketData(PacketDataSerializer packetdataserializer, int i, int j)
Now it's
public ClientboundLevelChunkPacketData(RegistryFriendlyByteBuf registryfriendlybytebuf, int i, int j)

I found a packet error with 1.20.5, I saw that the com.comphenix.protocol.wrappers.WrappedLevelChunkData$ChunkData class cannot be initialized because the constructor for the real packet changed. On 1.20.4 it was public ClientboundLevelChunkPacketData(PacketDataSerializer packetdataserializer, int i, int j) Now it's public ClientboundLevelChunkPacketData(RegistryFriendlyByteBuf registryfriendlybytebuf, int i, int j)

Oh I didn't notice the new RegistryFriendlyByteBuf that will need some major rework of the packet wrapper system since a bunch of packets require this new derivative to even read/create a new packet. I will look into it once I'm back from vacation. I would probably just use the new MinecraftRegistryAccess class from this PR for the registry accessor and rewrite some parts of the StructureCache to work with the new class.

1.20.5 support does not work on paper.