Getting at this type of info is one area where Mazda falls short.
The NAV Card used to come standard in the CX-5 trims, then for 2020 they made it an extra-charge option in all trims but the Signature (CX-5's top trim.) But when you looked at the CX-5 Build & Price section of Mazda's website, the NAV card was only listed as an Accessory in a couple of trims. I communicated with Customer Service on this months ago, and it's still not been fully corrected...and in this model, the NAV Card also drives Traffic Sign Recognition.
I just looked at the CX-30 section of the Build & Price website (likely where the OP was), and NAV is not mentioned anywhere on any trim...even the Premium. It's not listed in the features Summary section, and it is not is listed as an available Accessory on any of the trims (including the Premium.)
The
Mazda CX-30 promo site does not discuss NAV at all. They show the HUD with Speed Limit displayed, but there's no discussion as to some features being non-standard or how to get them.
As the OP stated, NAV is a feature that should be advertised. No one who is shopping for a car is even going to know that this is available, much less a component of every trim. And it drives the HUD, which is one of the slickest features of these cars, yet it's fallen between the cracks.