Using android phone as webcam by opencv 4.x version.

webcam.py

import urllib.request
import cv2
import numpy as np
import time
import requests

URL = "http://192.168.1.101:8080/shot.jpg"

while True:
    img_arr = np.array(
        bytearray(urllib.request.urlopen(URL).read()), dtype=np.uint8)
    img = cv2.imdecode(img_arr, -1)
    cv2.imshow('IPWebcam', img)

    if cv2.waitKey(0) & 0xFF == ord('q'):
        break

Warning: QT_DEVICE_PIXEL_RATIO is deprecated. Instead use:
   QT_AUTO_SCREEN_SCALE_FACTOR to enable platform plugin controlled per-screen factors.
   QT_SCREEN_SCALE_FACTORS to set per-screen DPI.
   QT_SCALE_FACTOR to set the application global scale factor.

solution:

export QT_DEVICE_PIXEL_RATIO=0
export QT_AUTO_SCREEN_SCALE_FACTOR=1
export QT_SCREEN_SCALE_FACTORS=1
export QT_SCALE_FACTOR=1