How to add .ttf fonts in PyQt6 using relative path?

Question

I am building an app and need to add a custom font of my desire in it, I have tried multiple ways to get that font loaded with a relative path but have failed with the error:

qt.qpa.fonts: Populating font family aliases took 192 ms. Replace uses of missing font family "ITCAvantGardeBk" with one that exists to avoid this cost. 

I am fed up of this error, suggest me some working ways of adding custom fonts using relative path and not absolute

These are my last attempts for getting the fonts loaded in my PyQt6 application using relative path

main.py

QFontDatabase.addApplicationFont("rsrc/ITCAvantGardeBk.ttf")
with open('styles.qss', 'r') as stlf:
    style = stlf.read()
    app.setStyleSheet(style)
# stylesheet = open('rsrc/vault8_styles.qss').read()
# app.setStyleSheet(stylesheet)
sys.exit(app.exec())

styles.qss

/* @font-face {
    font-family: ITC Avant Garde;
    src: url(rsrc/ITCAvantGardeBk.ttf);
} */

QLabel {
    font-family: 'ITCAvantGardeBk';
}

I have tried CodersLegacy's turn for adding fonts, this is how it went:

from PyQt6.QtWidgets import QApplication, QWidget, QLabel
from PyQt6.QtGui import QFont, QFontDatabase
import sys
 
class Window(QWidget):
    def __init__(self):
        super().__init__()
        self.resize(600, 300)
        self.setWindowTitle("CodersLegacy")
        self.setContentsMargins(20, 20, 20, 20)
 
        id = QFontDatabase.addApplicationFont("rsrc/ITCAvantGardeStd.ttf")
        if id < 0: print("Error")
        else: print("Success", id)
 
        families = QFontDatabase.applicationFontFamilies(id)
        print(families[0])
 
        label = QLabel("Hello World", self)
        label.setFont(QFont(families[0], 80))
        label.move(50, 100)
 
app = QApplication(sys.argv)
window = Window()
window.show()
sys.exit(app.exec())

Output:

ray@Ray project % /usr/local/bin/python3 "/Volumes/Alpha/Workspaces/Python/Projects/project-beta/project/test.py"
Error
Traceback (most recent call last):
  File "/Volumes/Alpha/Workspaces/Python/Projects/project-beta/project/test.py", line 24, in <module>
    window = Window()
  File "/Volumes/Alpha/Workspaces/Python/Projects/project-beta/project/test.py", line 17, in __init__
    print(families[0])
IndexError: list index out of range

However changing font path from relative to absolute spits out

Success 0
ITC Avant Garde Gothic Std

Now I want this, but with relative path-