MCProtocolLib is moving to the same packet names that Minecraft: Java Edition uses internally. There is some steps involved, but hopefully this guide helps.
This guide is not perfect and is only based on updating Geyser to the new packet names. Please reach out in the comments or on Geyser's Discord (https://discord.gg/geysermc) for assistance.
Handshake packet: com.github.steveice10.mc.protocol.packet.handshake.client.HandshakePacket -> com.github.steveice10.mc.protocol.packet.handshake.serverbound.ClientIntentionPacket
Login packets
Rename com.github.steveice10.mc.protocol.packet.login.server. to com.github.steveice10.mc.protocol.packet.login.clientbound.
Rename com.github.steveice10.mc.protocol.packet.login.client. to com.github.steveice10.mc.protocol.packet.login.serverbound.
Clientbound class renames:
LoginDisconnectPacket is now prefixed with Clientbound
LoginPluginRequest -> CustomQuery
LoginSuccess -> GameProfile
Serverbound class renames:
PluginResponse -> CustomQuery
Game data
Rename com.github.steveice10.mc.protocol.data.game.world. to com.github.steveice10.mc.protocol.data.game.level.
com.github.steveice10.mc.protocol.packet.ingame.clientbound.window.* -> com.github.steveice10.mc.protocol.packet.ingame.clientbound.inventory.*
com.github.steveice10.mc.protocol.packet.ingame.serverbound.window.* -> com.github.steveice10.mc.protocol.packet.ingame.serverbound.inventory.*
com.github.steveice10.mc.protocol.data.game.ClientRequest -> com.github.steveice10.mc.protocol.data.game.ClientCommand
com.github.steveice10.mc.protocol.data.game.chunk.Chunk -> com.github.steveice10.mc.protocol.data.game.chunk.ChunkSection
com.github.steveice10.mc.protocol.data.game.chunk.Column -> com.github.steveice10.mc.protocol.data.game.chunk.Chunk
com.github.steveice10.mc.protocol.data.game.entity.EntityStatus -> com.github.steveice10.mc.protocol.data.game.entity.EntityEvent
com.github.steveice10.mc.protocol.data.game.window.WindowAction -> com.github.steveice10.mc.protocol.data.game.inventory.ContainerActionType
com.github.steveice10.mc.protocol.data.game.window.WindowType -> com.github.steveice10.mc.protocol.data.game.inventory.ContainerType
com.github.steveice10.mc.protocol.data.game.window.**Param -> com.github.steveice10.mc.protocol.data.game.inventory.**Action
com.github.steveice10.mc.protocol.data.game.window.property.WindowProperty -> com.github.steveice10.mc.protocol.data.game.inventory.property.ContainerProperty
com.github.steveice10.mc.protocol.data.game.world.block.BlockChangeRecord -> com.github.steveice10.mc.protocol.data.game.level.block.BlockChangeEntry
com.github.steveice10.mc.protocol.data.game.world.effect.WorldEffect -> com.github.steveice10.mc.protocol.data.game.level.effect.LevelEvent
com.github.steveice10.mc.protocol.data.game.world.effect.ParticleEffect -> com.github.steveice10.mc.protocol.data.game.level.effect.ParticleEvent
com.github.steveice10.mc.protocol.data.game.world.effect.**EffectData -> com.github.steveice10.mc.protocol.data.game.level.effect.**EventData
com.github.steveice10.mc.protocol.data.game.world.notify.ClientNotivationValue -> com.github.steveice10.mc.protocol.data.game.level.notify.GameEventValue
com.github.steveice10.mc.protocol.data.game.entity.EntityStatus -> com.github.steveice10.mc.protocol.data.game.entity.EntityEvent
com.github.steveice10.mc.protocol.data.game.level.block.UpdatedTileType -> com.github.steveice10.mc.protocol.data.game.level.block.BlockEntityType
Anything in com.github.steveice10.mc.protocol.packet.ingame.serverbound.window moved to com.github.steveice10.mc.protocol.packet.ingame.serverbound.inventory and any usage of windowId / getWindowId() was replaced with containerId / getContainerId()
com.github.steveice10.mc.protocol.data.game.world.notify.ClientNotification -> com.github.steveice10.mc.protocol.data.game.level.notify.GameEvent
Ingame packets
Rename com.github.steveice10.mc.protocol.packet.ingame.server. to com.github.steveice10.mc.protocol.packet.ingame.clientbound.
Rename com.github.steveice10.mc.protocol.packet.ingame.client. to com.github.steveice10.mc.protocol.packet.ingame.serverbound.
Rename com.github.steveice10.mc.protocol.packet.ingame.clientbound.Server to com.github.steveice10.mc.protocol.packet.ingame.clientbound.Clientbound
Rename com.github.steveice10.mc.protocol.packet.ingame.serverbound.Client to com.github.steveice10.mc.protocol.packet.ingame.serverbound.Serverbound
Rename com.github.steveice10.mc.protocol.packet.ingame.clientbound.world. to com.github.steveice10.mc.protocol.packet.ingame.clientbound.level.
Rename com.github.steveice10.mc.protocol.packet.ingame.serverbound.world. to com.github.steveice10.mc.protocol.packet.ingame.serverbound.level.
Clientbound class renames:
AdvancementTab -> SelectAdvancementsTab
Advancements -> UpdateAdvancements
BossBar -> BossEvent
DeclareCommands -> Commands
DeclareRecipes -> UpdateRecipes
DeclareTags -> UpdateTags
Difficulty -> ChangeDifficulty
JoinGame -> Login
PlayerListEntry -> PlayerInfo
PlayerListData -> TabList
PluginMessage -> CustomPayload
Statistics -> AwardStats
UnlockRecipes -> Recipe
PlayerActionAck -> BlockBreakAck
PlayerChangeHeldItem -> SetCarriedItem
PlayerHealth -> SetHealth
PlayerPositionRotation -> PlayerPosition
PlayerSetExperience -> SetExperience
SpawnEntity -> AddEntity
SpawnExpOrb -> AddExperienceOrb
SpawnLivingEntity -> AddMob
SpawnPainting -> AddPainting
SpawnPlayer -> AddPlayer
EntityAnimation -> Animate
EntityAttach -> SetEntityLink
EntityCollectItem -> TakeItemEntity
EntityEffect -> UpdateMobEffect
EntityEquipment -> SetEquipment
EntityHeadLook -> RotateHead
EntityMetadata -> SetEntityData
EntityPositionRotation -> MoveEntityPosRot
EntityPosition -> MoveEntityPos
EntityProperties -> UpdateAttributes
EntityRemoveEffect -> RemoveMobEffect
EntityRotation -> MoveEntityRot
EntitySetPassengers -> SetPassengers
EntityStatus -> EntityEvent
EntityTeleport -> TeleportEntity
EntityVelocity -> SetEntityMotion
VehicleMove -> MoveVehicle
DisplayScoreboard -> SetDisplayObjective
ScoreboardObjective -> SetObjective
Team -> SetPlayerTeam
UpdateScore -> SetScore
BlockBreakAnim -> BlockDestruction
BlockChange -> BlockUpdate
BlockValue -> BlockEvent
ChunkData -> LevelChunkWithLight
Explosion -> Explode
MapData -> MapItemData
MultiBlockChange -> SectionBlocksUpdate
NotifyClient -> GameEvent
PlayBuiltinSound -> Sound
PlayEffect -> LevelEvent
PlaySound -> CustomSound
SpawnParticle -> LevelParticles
SpawnPosition -> SetDefaultSpawnPosition
UnloadChunk -> ForgetLevelChunk
UpdateLight -> LightUpdate
UpdateTileEntity -> BlockEntityData
UpdateTime -> SetTime
UpdateViewDistance -> SetChunkCacheRadius
UpdateViewPosition -> SetChunkCacheCenter
CloseWindow -> ContainerClose
OpenHorseWindow -> HorseScreenOpen
OpenWindow -> OpenScreen
SetSlot -> ContainerSetSlot
TradeList -> MerchantOffers
WindowItems -> ContainerSetContent
WindowProperty -> ContainerSetData
Serverbound class renames:
PluginMessage -> CustomPayload
Request -> ClientCommand
Settings -> ClientInformation
AdvancementsTab -> SeenAdvancements
CreativeInventoryAction -> SetCreativeModeSlot
ClickWindowButton -> ContainerButtonClick
CloseWindow -> ContainerClose
MoveItemToHotbar -> PickItem
SetBeaconEffect -> SetBeacon
UpdateCommandBlockMinecart -> SetCommandMinecart
UpdateCommandBlock -> SetCommandBlock
UpdateJigsaw -> SetJigsawBlock
WindowAction -> ContainerClick
TeleportConfirm -> AcceptTeleportation
SteerBoat -> PaddleBoat
SteerVehicle -> PlayerInput
UpdateSign -> SignUpdate
VehicleMove -> MoveVehicle
PlayerChangeHeldItem -> SetCarriedItem
PlayerInteractEntity -> Interact
PlayerPlaceBlock -> UseItemOn
PlayerPosition -> MovePlayerPos
PlayerPositionRotation -> MovePlayerPosRot
PlayerRotation -> MovePlayerRot
PlayerState -> PlayerCommand
PlayerSwingArm -> Swing