You're recommended to use OWC's free software to verify your external drive is fast enough to store ProRes video recordings made with your USB-C iPhone.
ProRes
How to record ProRes video on iPhone or onto an external drive
Learn how to use your iPhone to record ProRes videos on its internal storage or directly to an externally connected storage device like a USB thumb drive.
The M2 iPad Pro captures ProRes video and brings a new Apple Pencil hover gesture
Apple's new M2 iPad Pro features ProRes video capture, a new hover gesture for Apple Pencil and more. It's launching in stores on October 26.
iCloud for Windows gains support for Apple ProRes videos, ProRAW photos and more
Apple has updated iCloud for Windows, with version 13 now available with support for Apple ProRes videos, Apple ProRAW photos, strong password generation and more.
Apple ProRes video support not arriving in time for iPhone 13 Pro launch
Support for ProRes on the iPhone 13 Pro and Max models won't be available at the September 17 launch of the handsets. Instead, ProRes video support will be arriving at a later date.
In addition to a portrait video mode, iPhone 13 could also support Apple’s ProRes codec
Aside from a previously rumored portrait video mode, this year's upcoming iPhone 13 models releasing in the fall are understood to also add support for Apple's ProRes video codec.