ACharacter::Landed not called on Simulated proxies

Create a custom CharacterMovementComponent and override SetPostLandedPhysics:

void UShooterCharacterMovement::SetPostLandedPhysics(const FHitResult& Hit)
{
	// call for non-authority only because this is already called for authority elsewhere
	if (CharacterOwner && CharacterOwner->GetLocalRole() != ROLE_Authority && CharacterOwner->ShouldNotifyLanded(Hit))
	{
		CharacterOwner->OnLanded(Hit);
	}
	Super::SetPostLandedPhysics(Hit);
}