That not something the Public API provides
Get About Me Bio or Status

I somehow got to implement the oauth myself, now I can verify a username.
But yes, for those who don't wanna use oauth implementation, those visitors asking for help in the future, the public API provides the location undefined if no location in user's profile and you can say the user to set location to your discord username and then use public API to verify location matches discord username to verify a chess.com user.
I need to know a user's status or about me (bio) to get their discord. For vertification purposes I can say like "Set your chess.com profile status to your discord username." but I checked all Chess.com Unofficial API and there was status but it was account status (staff, closed, etc.)