The Switch needs an update to support WPA3. It currently shows them greyed-out, attempting to connect shows the following error message:
https://i.imgur.com/6SxNdcp.jpg
The Switch does support WPA3 Transition Mode, but running in transition mode instead of pure WPA3 sacrifices security since hackers can attack the network using WPA2.
The longer Nintendo takes to push a software update for WPA3 compatibility, the longer those of us with Switches will need to hold off on fully migrating to WPA3.