Shoot, that should be counted as done when you talk to the King for the first time. I'll have that fixed next patch, and it'll also be counted as done if you have a regular chat with him again.
Minor Spoilers below:
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Ferdinn would love to talk more about his niece, but as one NPC mentioned, he's still single. Unfortunately, that means the succession is still uncertain, which could make a conversation potentially dangerous for her- especially since Astra herself is involved in some vaguely Project-Balor-related drama that caused her to run away from home.