I’ve not found a way to do this. I have two SanDisk drives. One is has USB C + A connections, the other has USB A + Lightning and came with a USB-A to USB-C connector.
The C+A drive is formatted with encrypted APFS which can be read by my iPad Pro and Mac, but not my iPhone. This is the drive I use for sensitive files.
AFAIK the iPhone cannot recognize an external drive unless it is formatted FAT32 or ExFAT, with a Master Boot Record. So my C+A+Lightning drive is formatted ExFAT and I use it for non-sensitive files, backing up my photos, etc.
SanDisk does include security software which I immediately erased. I have never used any software of this type that I have not personally tested.
Software like this may allow you to accomplish your task. Please let us know if you are successful. Good luck.