I am sure that this is yet another macOS Catalina+ tcl/tk problem.  3.10 is fine on Mohave.  Those complaints must come from macOS in response to 'Client' tk requests.  IDLE and tkinter do not use those names.  If you want to try to see what tkinter function triggers those messages, try the following in the Python REPL.

import tkinter as tk
from tkinter import font
root = tk.Tk()
fnames = font.names(root)
f1 = font.Font(root=root, name=fnames[0], exists=True)
f2 = font.Font(root=root, name='TkFixedFont', exists=True)