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Behind the scenes, the mobile uSDKs perform exactly the same routine as the browser one does - calling SupportedVersionsController#/api/v2/supported-versions and then AuthenticationController#/api/v2/auth. These are also good places to set a breakpoint and review the flows.
Changelog
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[6.4.77-rel.5] - 12/18/2020
Updates to support uSDK 6.4.77