In the past, iTunes could be used to install iOS apps downloaded via Mac into iOS devices, but this feature was slowly purged from iTunes. As first, Apple removed capability to import iOS apps installers from iOS device to Mac, but apps could be still downloaded to iTunes Library manually from integrated iOS App Store. Unfortunately, this feature was dropped too, so the only way to install apps on iOS devices is to download them directly on iOS device from built-in App Store app or to use 3rd party solutions like iMazing 2. We covered this issue HERE. Apple still provides this version of iTunes HERE.
Alongside iTunes 12.7 without App Store, Apple released iTunes 12.6.3 with App Store, which was updated twice – to version 12.6.4 and later 12.6.5. This special edition of iTunes does not work on macOS Mojave – it fails to install.
If you rely on iTunes with App Store, do not install macOS Mojave. It’s unclear, if Apple dropped support, or this special edition of iTunes was not been yet updated to work with macOS Mojave.