How can an iOS app offer opt-in advertising?

How can an iOS app offer opt-in advertising? I understand that Unity, for example, allows developers to offer users an opt-in to view advertising.

opt-in? Why would users subject themselves to ads given the choice?


I'd guess the usual approach is ads enabled by default, with the ability to opt-out/no ads via IAP.

How can an iOS app offer opt-in advertising?
 
 
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