The recent High Sierra MacOS update brings us iTunes 12.7 which loses the ability to purchase apps for iPads associated with an Apple ID from within iTunes. There are convoluted methods of downgrading iTunes 12.7 to 12.6 to regain that capability, but it’s a pain to keep preventing Apple’s updates from forcing a user to lose this capability.
For most individual users, this isn’t much of an issue, but for institutional users, it makes it more complicated to acquire and distribute apps to iPads.
My solution is to build a VirtualBox machine with an original (un-updated) High Sierra MacOS with iTunes version 12.6. Whenever I need to access an Apple ID tied to a specific iPad account, I just fire up the MacOS VirtualBox, log into the associated iTunes account, acquire the needed app(s), and then log out. Since I have the iPads set up to auto-download apps purchased with the account, the apps typically show up on the device without additional intervention.
Let me know if you could benefit from a clone of my MacOS machine or need additional guidance on using VirtualBox.