I was also curious, so I web-searched it for you and came up with a couple of promising items: A USB Voltmeter with E-marker and protocol testing: https://www.

I was also curious, so I web-searched it for you and came up with a couple of promising items: A USB Voltmeter with E-marker and protocol testing: https://www.amazon.com/ChargerLAB-KM003C-Portable-Charging-Voltmeter/dp/B0BJ24PVNJ/ https://www.amazon.com/ChargerLAB-KM003C-Portable-Charging-V... A very basic but maker-friendly signal/capability tester: https://www.tindie.com/products/petl/usb-c-cable-tester-c2c-caberqu/ https://www.tindie.com/products/petl/usb-c-cable-tester-c2c-...