I think Switch user's will most likely need to use the Wii's USB wired Ethernet network connection adapter on the TV dock or Switch's USB ports for going online if they don't want to use Wireless/Wi-Fi.
There is also a chance that the Wii's USB network adapter would not work on the Switch because Nintendo did not include the USB Network adapter's software drivers for the Switch to save space on the internal storage drive, or the Wii's USB wired network adapter does not work on the Switch because of compatibility problems.
There is also a chance that the Wii's USB network adapter would not work on the Switch because Nintendo did not include the USB Network adapter's software drivers for the Switch to save space on the internal storage drive, or the Wii's USB wired network adapter does not work on the Switch because of compatibility problems.