Measuring the voltage between Cerbo's Ethernet, USB or HDMI shells and the negative DC pole, I see a voltage difference on the order of 100 mV. I varies, but the difference is never 0.
Are the connectors' shells/ground on the same potential as DC negative?
Would it cause harm to bring the connector's GND to a common ground (e.g. earth or DC negative)?
With a standardized potential, connections problems based on different potential issues (e.g. https://community.victronenergy.com/questions/147472/probleme-mit-mehreren-usb-rs485-verbinungen-am-hos.html) would not exist and the need for costly galvanic isolation devices would also drop.