How to kill a thread which running a Tkinter code?

Question

I am trying to run a code that checks for Bluetooth connection if that particular connection is not there then the white screen will appear. for that, I am written Tkinter code and I am trying to control that white screen using multithreading but when I am killing the thread popup is not diapearing.

# Python program using 
# traces to kill threads 

import sys, threading, time 
from tkinter import *
from tkinter import messagebox

class TraceThread(threading.Thread): 
    def __init__(self, *args, **keywords): 
        threading.Thread.__init__(self, *args, **keywords) 
        self.killed = False
    def start(self): 
        self._run = self.run 
        self.run = self.settrace_and_run
        threading.Thread.start(self) 
    def settrace_and_run(self): 
        sys.settrace(self.globaltrace) 
        self._run()
    def globaltrace(self, frame, event, arg): 
        return self.localtrace if event == 'call' else None
    def localtrace(self, frame, event, arg): 
        if self.killed and event == 'line': 
            raise SystemExit() 
        return self.localtrace 
def func(): 
    
    root=Tk()
    l1=Label(root,text="please wait connection",width=200,font='Helvetica 22 bold').place(x=-1000,y=400)
    root.overrideredirect(True)
    root.overrideredirect(False)
    root.attributes("-fullscreen", True)
    root.mainloop()

t = TraceThread(target=func) 
t.start() 
time.sleep(2.5) 
t.killed = True  # sends a SIGTERM
t = TraceThread(target=func) 
t.start() 
time.sleep(2.5) 
t.killed = True  # sends a SIGTERM

            

if anyone got any way to kill it please share Thank you