Apple has announced that it will be discontinuing iTunes U and iBooks Author, iBooks Author will be transitioned to pages and will no longer be updated.
Apple is discontinuing iTunes U by the end of 2021 and it will no longer function after this date, you can see more details from Apple on this below.
iBooks Author will no longer be updated, and it won’t be available to new users as of July 1, 2020. If you’ve previously downloaded the app, you can still access it from your App Store purchase history. You can continue to use iBooks Author on macOS 10.15 and earlier, and books previously published to Apple Books from iBooks Author will remain available.
You can find out more details about what is happening with iTunes U and iBooks Author over at Apple at the link be;low.
Source Apple, 9 to 5 Mac, Techmeme