The Steam Deck’s hardware is Linux compatible, which Valve obviously paid attention to during development. The same applies to Steam OS and the drivers, everything is coordinated with each other. This has nothing to do with your Topton hardware and your built-in USB-C port.
That was to be expected.
The Topton Consumer Mini PCs do have USB-C/Thunderbolt, but (as far as I can see) are only available with Windows (obviously the hardware is designed for this).
The Topton Industrial Mini PCs are delivered with Linux and BSD, but they don’t have USB-C, only HDMI and DP for video output.
Can you test the USB-C port directly with a USB-C monitor (without a hub)?
Is there a BIOS update for the PC? If so, flash it and test it.
Otherwise, I would recommend testing different live distributions: