When to show tracking permission pop up?

With the iOS privacy changes I'm a bit confused when we need to show the privacy pop up to request permission, and what needs to be gated behind the answer?

We use mixpanel/ga, and from my reading of the iOS 14 documents it seems we may need to ask permission, even if the IDFA is not used. Is this the correct interpretation?
When to show tracking permission pop up?
 
 
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