A Bitaxe Gamma is not detected when connected to an upstream USB-C port. Presumably, this is due to lack of pull-downs on the Bitaxe's USB-C CC pins. USB Sources detect the attachment of devices through USB-C physical connections by utilizing the CC pins.

I have verified this behavior on both a modern MacBook Air and a Linux server with USB-C ports. Presumably, this would also be an issue with hubs that have USB-C ports facing downstream.

There is no issue when a Bitaxe is connected via a USB-C to USB-A cable, because USB-A ports detect attachment via devices pulling up D+ and or D- (in the Bitaxe's case, internally in the USB controller).