Using Apple Configurator 2
Download an app from App Store to you phone
Open Apple Configurator 2 on your Mac and log into your Apple account
Connect your phone to your Mac using a USB cable
Into Apple Configurator 2 select your phone
Then tap on the “Add” button in the top, then tap on “Apps” button
Choose the app and tap on “Add” button
Finally it could tell you an app already exists, but don’t worry — just be in a hurry to grab an .ipa using this path:
~/Library/Group\ Containers/K36BKF7T3D.group.com.apple.configurator/Library/Caches/Assets/TemporaryItems/MobileApps/