We have the Facebook SDK and Facebook is saying that we should use their SDK to make the SKAdNetwork calls. Is this required?

No. While the Facebook SDK is one option advertisers can use to implement the SKAN methods necessary for Facebook's iOS 14 campaign measurement, apps can continue to use another third party (including the Branch SDK) for that functionality.

In particular, you should only use one method to call update conversion value, as making dual calls can get messy. While Facebook offers functionality within the Facebook Events Manager to map conversion value events, Branch provides equivalent functionality via an API endpoint that advertisers provide to Facebook for syncing a Conversion Bit Schema, with the advantage that the mapping from Branch can easily be used by networks aside from Facebook.

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