Microsoft has been working with the iOS ecosystem and continues to work with Apple to provide the best possible platform for users and enterprises to work hand in hand. Microsoft has ensured their flagship products are available through the Apple Store as shown below

With Microsoft Intune we have 4 methods of deployment;
iOS App Protection Policies (APP) Managed
This solution is targeted for BYOD devices that are not enrolled but access corporate data from the approved corporate apps, for example; Outlook, Word and Excel. App Protection Policies are placed on the applications that are accessing corporate data to ensure the security requirements are met.
More information can be found via the following url about App Protection Policies. https://docs.microsoft.com/en-us/intune/apps/app-protection-policy
User Enrollment
User Enrollment has been designed with the BYOD user in mind, this enrollment allows administrators enforce Password Restrictions, restrict viewing non-corporate documents in corporate apps, restrict viewing corporate documents in unmanaged apps, require encrypted backup and automatically removed apps if the device is unenrolled.
Device Enrollment
Device enrollment is user-initiated through the company portal and is the most common method of enrolling corporate devices. This option provides the largest range of MDM capabilities available within Microsoft Endpoint Manager.
Automated Device Enrollment
Automated device enrollment is designed for corporate-owned devices synced to Microsoft Endpoint Manager via Apple Business Manager. This enrolled provides supervised-mode MDM capabilities, Secure Kiosk, Classroom device and Lock management to a device.
Regards,
The Author – Blogabout.Cloud