USB isolators (single port) can be bought cheaply on eBay but may be bandwidth limited. They use a small isolated DC-DC brick and a USB isolation chip, probably with internal isolation capacitors to get the signals across
I think the ADI ones are actually based on transformers.
Specifically they'll do "Full Speed" 12Mbit, but not "High Speed" 480Mbit. USB3 @ 5Gbit can also be isolated, as it uses separate send/receive pairs. But that doesn't mean you can use a hub and drop down to 480MBit - they're separate data paths.
If you need 480Mbit, the best solution is probably a Raspberry Pi or other SBC, to convert to ethernet.
Specifically they'll do "Full Speed" 12Mbit, but not "High Speed" 480Mbit. USB3 @ 5Gbit can also be isolated, as it uses separate send/receive pairs. But that doesn't mean you can use a hub and drop down to 480MBit - they're separate data paths.
If you need 480Mbit, the best solution is probably a Raspberry Pi or other SBC, to convert to ethernet.