Proper cables
Based on tracker#1258200, we should state somewhere near "first setup" this warning/information:
Make sure you use proper Gigabit Ethernet cables i.e. Cat 5e or Cat 6 straight unshielded twisted pair cables with 8 wires (8P8C) to connect your devices to the Turris as well as your Turris to the modem or other ISP device.
exact wording could be improved