I wouldn't call that "slightly" unround. I would contact a frame builder about this, looks like it too much to just fix by reaming it.
FWIW, the photo (and how I have positioned the steerer) does exaggerate the issue.
Will seek professional advice, and I have also asked the seller if they have personally had a headset in there.
@kjlem started
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I wouldn't call that "slightly" unround. I would contact a frame builder about this, looks like it too much to just fix by reaming it.