I am the Register reviewer.
I tested with 2 different USB-C docks and a USB-C to HDMI monitor cable. They're the only ones I have.
One is from a Gemini PDA and has USB-A, USB-C and Ethernet. I think I did not test Ethernet but I can do that. The dock contains an Ethernet controller: it's a USB-attached Ethernet card, effectively. It works on Android, macOS, Windows, Linux, etc.
As far as I recall the FLX1 detected the Ethernet port but I didn't test it.
The other dock has audio, various sizes of USB, and HDMI out. All the ports worked except display. You can drive the phone with a full sized keyboard and mouse, which is amusing but useless. You can power the phone from the dock while in use.
But it can't drive a display, which is a damned shame and a deal-breaker for the form-factor. Otherwise this could be a real PC in your pocket.
The company told me it was working on wireless display support but I do not own any wireless displays to test with.