How to use PyQt6 in Blender

blender_pyqt6.py

# tip: you can run Blender using an alternative Python environment to get access to PyQt6
# for example I created a conda environment with PyQt6 installed, then executed blender with these args:
# ~/Downloads/blender-3.4.1-linux-x64/blender --env-system-python /home/iyad/miniconda3/envs/pyqt6/

from PyQt6.QtWidgets import QApplication, QLabel
import bpy

# Process Qt event loop using a Blender timer
# note we do not use app.exec() at the end of the script, it will block Blender
def event_loop_timer():
    QApplication.processEvents()
    return 0

# Only create a QApplication if there are no other instances of QApplication
# otherwise it crashes as only one instance of QApplication is allowed by Qt
if QApplication.startingUp():
    app = QApplication([])
    bpy.app.timers.register(event_loop_timer)

label = QLabel("Qt inside Blender!")
label.show()