"MISSING LABEL PropertyFile - val Activity" error when creating report types

Feed posts for Task and Event cannot be used for custom report types. When attempting to create a custom report type using Activity as the primary object and relating it to the Activity Feed object (API Name: ActivityFeed), the object name is displayed as "MISSING LABEL PropertyFile - val Activity not found in section StandardFeedLabel" and an error occurs upon saving.

There is no direct feature to include these feeds in report types; however, you can export the relevant data using Data Loader as a workaround. In Data Loader, select [Task Feed (TaskFeed)] or [Event Feed (EventFeed)] as the object to export and proceed with the data export.