Both USB-C and Lightning systems use the USB hardware layer and it has been possible to use USB2.0 products on a USB-C port so we know that is possible. The problem is the software running on the host and the Apple Lightning Authentication/ID chip that controls power to the accessory. The iPad Pro 2021 does not provide the option to add USB drivers so the accessory needs to be of a supported type that the iPad can work with using its built in drivers. This should also not be a problem as the iPad needed similar for the FLIR camera in its lightning configuration. The problem would likely be the authentication/ID chip that resides within the accessory, in this case the camera dongle. That chip not only identifies the accessory as a legitimate Apple approved product to the iPad OS, but it also controls the power supply to the accessory. It has been shown that the power control element of the authentication chip may be bypassed by applying power to the accessory from the available power pin on the lightning connector.
The question has to be, does the new iPad USB-C hardware/software configuration still require an authentication/ID chip in accessories?
Well we know that the iPad Pro USB-C port will work with a standard USB-C keyboard but that it does not permit use of a USB-C memory stick as memory expansion (except for photo import/export) so the port is not exactly predictable in terms of its functionality, thanks to the iPad iOS operating system configuration. If an Authentication/ID chip is still supported, is it the same as the Lightning port in terms of its ID functionality etc ?
If the Authentication/ID chip is no longer needed, it may be possible to bypass it in the FLIR camera so that the camera is basically standard USB with Apple iOS version Firmware. Then it might be possible to connect the USB camera to the USB-C port with a common adapter to see whether the iPad iOS will recognise it and apply a suitable driver. Then there is the question of whether the FLIR app for the camera can be installed on the iPad as the Apple App Store may claim incompatibility with the USB-C equipped iPad Pro.
So many unknowns and little information to work with