I’m using a number of Teckin Smart Plugs in my home which are 2.4GHz based. With WPA3 enabled on Eero Pro6 none of them will connect. As soon as I turn WPA3 off they work fine. 

Turning off 5GHz and enabling legacy mode has no effect but toggling WPA3 off works consistently. 
 

Even with a factory reset of the plugs they don’t work with WPA3 enabled on Eero. I.e. A customer would not be able to do a first time installation of one of these plugs.