Android 12 (API 31) comes with new features and API changes.
All of the behavior changes are well-documented on the Android Developer platform - Android 12 Behavior changes.

Using Unity iOS on Xcode 12.3 with the New Build System will throw a build-time error:
"Building for iOS, but the linked and embedded framework 'Leanplum.framework' was built for iOS + iOS Simulator."

Apple is changing the information that is required when submitting new apps and app updates, starting December 8, 2020. Information about the app's privacy practices, integration, and data collection needs to be provided in App Store Connect.

Starting from iOS 14, there are changes in the Advertising, and using the IDFA now requires user consent. You can read more in the iOS 14 Updates article.

iOS 14 comes with new features and a new focus on user privacy. It introduces a new way of dealing with IDFA identifiers and tracking of users across sessions and apps.
Important changes:

Starting from Leanplum iOS SDK version 2.7.0 there are changes to the in-app messages templates. The templates are now separated and in their own files.
Previously all templates were in the LPMessageTemplates.h and LPMessageTemplates.m files which were downloadable with the SDK.

Leanplum iOS SDK version 3.0.0 releases a number of improvements for Swift.
There are several classes, methods, and parameters that have been changed to be more Swift friendly.

With the latest update to iOS 13, Apple introduced changes to push token data, location permissions, and Bluetooth settings. In response, Leanplum has made changes to our SDK and for this to continue to work, you will need to update to the latest version of our SDK. Below are the changes you will see in each area.

See Leanplum's latest SDK release notes: