Solution:

import tkinter as tk

def fun():
    label_frame.config({"labelwidget":titulo})

root = tk.Tk()
root.geometry("300x100")
label_frame = tk.LabelFrame(root)
label_frame.pack(pady=10)

titulo = tk.Label(label_frame, text="Titulo lol?")
titulo.pack(side="top")

str_var = tk.StringVar()
entrada = tk.Entry(label_frame, textvariable = str_var)
entrada.pack()

boton = tk.Button(label_frame, text="Push me!", command=fun)
boton.pack()

root.mainloop()

I did not know how to do this until a few minutes ago xD, it's something basic maybe, but there may be someone who wants to know, how can this be done

Result:

Before

After