Please check the release notes at GitHub for the list of new features and changes to the existing features of OroPlatform application.
The CHANGELOG.md files of the individual packages comprising this application describe significant changes in the code that may affect the upgrade of your customizations.
You can use the following command to find all CHANGELOG.md files in Oro packages:
find -L vendor/oro -maxdepth 2 -type f -name CHANGELOG.md