I wonder if I accidentally somehow ended up with a usb2 connection instead of usb3 and that's actually the source of the slowness of this operation

and by slowness I mean it's writing "mere" gigabytes per minute

let's be honest it's a pretty wild world to be in where you say "mere gigabytes per minute"

@cwebber I've had somewhat better luck with pv and writing media like that. Partly because getting the right block size on modern media is a bit of a pain.