For a while, Apple had released a version of iTunes – 12.6.5 – that still had the App Store, so businesses could manage apps on their devices. With the release of macOS Mojave, this iTunes version no longer works, so the workaround that Apple had provided to allow some users to still download and manage apps from the desktop is now dead.
So there is one other solution: iMazing can download, install, and manage apps for iOS devices. Check out the linked article for more. I’d still rather have the App Store accessible from the desktop, but this is a solution that can be useful for many people.
Full disclosure: I do writing work and screencasting for iMazing.