Disk utility for iPad Pro
How can I encrypted my ssd or HDD through iPad Pro?
iPad Pro, iPadOS 16
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iOS/iPadOS does not support connection of encrypted USB media devices, with one exception - this being an APFS encrypted volume. APFS is Apple Proprietary.
APFS volumes can only be created/formatted by a Mac computer - and are not compatible with Microsoft Windows, Linux, Android or other computers.
iPad does not provide any facilities to format an external storage device. Formatting must be performed using an appropriate computer, such as Windows PC or Mac. Some devices, such as Cameras, can format memory cards. To be recognised by iPadOS, the attached USB storage device must be formatted to FAT, FAT32, exFAT, APFS or HFS+ with a single partition. Microsoft NTFS and other proprietary device formatting are not supported.
More information about connection to external devices and storage can be found in the iPad User Guide - along with other frequently overlooked information about your iPad and iPadOS:
Connect external storage devices to iPad - Apple Support