You'll need to make the FirstPersonPlayer a ghost component and synchronize the ControlledCharacter field. This will ensure that the entity references set up by the server when instantiating a character will be carried over to clients:
[GhostComponent]publicstructFirstPersonPlayer:IComponentData{[GhostField]publicEntityControlledCharacter;}Then, make FirstPersonCharacterComponent a ghost component and synchronize the ViewPitchDegrees field:
[GhostComponent]publicstructFirstPersonCharacterComponent:IComponentData{// ...[GhostField]publicfloatViewPitchDegrees;}