Just to emphasize how important grounding is..
I have two Ethernet to Fiber adapters, a modem, router and VOIP phone box.
I started feeling a strange sensation holding the phone to my head so I measured and it was 100V/M at the ear on my corded phone.
Unplugging the two fiber boxes turned out to reduce to 20V/M. The boxes look like this:
https://www.trendnet.com/products/ethernet-fiber-converter/TFC-110S30iThankfully, they have a shiny silver knob that can be unscrewed and a wire wrapped around, then screwed back in. Upon grounding, the phone now measures 10V/M at the ear.
Since routers are plastic these days, there is no way to ground them, but if you can find a metal router that can be grounded, it will likely help a lot, and even provide a ground to any device plugged into it that uses only two prongs.. like a laptop.
I only use fiber with USB adapter, no ethernet, the difference can be picked up with a small radio. Even shielded ethernet cable emits enough to be picked up meters away, not sure why... There was nothing else I picked up so far away as I did ethernet cable.