Nondetection protects you from divination magic.
In an early post on Sage Advice, I read Nondetection + Invisibility even protects against True Seeing. Okay, makes sense.
But what about the Divination Wizard's Third Eye ability? It doesn't read that you cast a spell or in particular that you are using magic on yourself. It only mentions that you use an action and increase your powers of perception. As such, there's no magic involved, correct? And as such these powers could perceive through invisibility + nondetection?
It would make sense to treat it as magical, but at the same time I've always wondered why the sight ranges seemed severely limited compared to their spell-based counterparts. Perhaps this is why? Hoping for answers based on RAW only or Mike Mearls/Jeremy Crawford posts. (Links please.)