Wired Connection Preference
In Smash 6, if the console is currently connected to the internet via a wired connection, an option becomes available that allows the player to restrict matchmaking to only other players who are also on a wired connection.
Notes
A long requested feature since Wi-Fi doesn't have the stability of a wired connection.
Players on a wired connection generally prefer a longer queue time than playing on an unstable connection.
The majority of players are still going to be playing on Wi-Fi.