We are making app for employees of some company. They have 100 000+ employees in several countries (China, Philippines, India, Europe...). Now we are making iOS app which will be used by those employees and we need to distribute it. App Store is not an option for us since it is in-house app. We need some simple process as there is on App Store so the user can just visit some link once, install the app and get OTA updates (as we update the app regularly) without any setup or registration. According to my understanding of very complex and scattered Apple manuals for various app distribution methods, it seems that only viable solution for us is MDM.
Is it possible to use the MDM like described above? User devices are employees personal phones, we don't have and we don't want any control over the device (wiping memory, controlling if our app runs or if the device is online...) all we need is simple Apple Store-like process for users to get the app and OTA upgrades (so the user doesn't have to click a link or do anything to get an update).
If you are building iOs app, then Apple Developer Enterprise Program is solution for your problem. We had similar experience, but with smaller company.
As the result you will get one simple link - that can be posted on web-site or send through email. And anyone can download and install it on iPhone/iPad. Please check simplest version here.
To make app self-downloaded (aka OTA), you have to include inside app small checking the plist (or any other file from server). Please check it here, here and here