If you want to continue to use iTunes to download and manage iOS apps and ringtones for your devices, Apple has quietly released version 12.6.3, which can replace the latest version 12.7, which removed those features. Both versions support iOS 11 and iPhone 8/8 Plus/X models, according to this announcement on Reddit.
The snag is that it uses the older version of the iTunes Library, not the newer version created by iTunes 12.7. So if you want to use it, you’ll need to either revert to a backup made prior to installing 12.7, or launch the 12.6.3 app with the Option key held to create a new library.
Apple has used some interesting settings to support installation of 12.6.3. This ‘older’ version can be installed over 12.7, and is seen by the App Store app as being ‘newer’ than 12.7. However, you can still install version 12.7 from its standalone installer.
iTunes 12.6.3 runs on Yosemite, El Capitan, Sierra, and High Sierra.
Apple made version 12.6.3 available here in an announcement for enterprise management on 23 September, ten days after releasing the 12.7 update. It has not made any attempt to publicise this version more widely, though, indicating that it wants users to stick with 12.7, and for 12.6.3 to be used only by “certain business partners” where the features removed in 12.7 had caused a serious problem.
Apple seems to have responded to outcry from “certain business partners”, but not to ordinary users.
You can download the Mac and two PC versions from their links here. iTunes 12.6.3 is not available from the App Store, though.
(Thanks to Miles Wolbe for very kindly drawing attention to this.)