Internal pull-up resistors not working

[MinePro120]

Consider the 3 following scripts :

1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#!/bin/python3

from gpiozero import Button
import time
import os

stopButton = Button (17)

while True:
     if stopButton.is_pressed:
         os.system ("sudo shutdown now -h")
     time.sleep (1)
exit (1)
2~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#!/bin/python3

import RPi.GPIO as GPIO
import os
import time
from threading import Thread

GPIO.setwarnings (False)
GPIO.setmode (GPIO.BCM)
shutdown_pin = 26
GPIO.setup (shutdown_pin, GPIO.IN, pull_up_down=GPIO.PUD_UP)

def shutdown_check():
        while True:
                pulsetime = 1
                GPIO.wait_for_edge (shutdown_pin, GPIO.FALLING)
                print ("falling detected")
                time.sleep (0.01)
                while GPIO.input (shutdown_pin) == GPIO.LOW:
                        time.sleep (0.01)
                        pulsetime += 1
                if pulsetime >=2 and pulsetime <=3:
                        os.system ("sudo reboot")
                elif pulsetime >=4 and pulsetime <=5:
                        os.system ("sudo shutdown now -h")
try:
        t1 = Thread (target = shutdown_check)
        t1.start ()
except:
        t1.stop ()
        GPIO.cleanup ()
        exit (0)
3~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#!/bin/python3

import RPi.GPIO as GPIO
import time
import os

GPIO.setmode (GPIO.BCM)
GPIO.setup (17, GPIO.IN, pull_up_down = GPIO.PUD_UP)

def Shutdown (channel):
    print ("Shutting down...")
    os.system ("echo $(date) >> shutdown.log")
    time.sleep (3)
    os.system ("sudo shutdown now -h")
    exit (0)

GPIO.add_event_detect (17, GPIO.FALLING, callback = Shutdown, bouncetime=2000)

while 1:
    time.sleep (1)
exit (1)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The above scripts are common shutdown scripts that can be found on the web, utilizing an NO pushbutton connected to GPIO 26 and ground (physical 37). None of the above scripts work though, since the internal pull-up resistors don't seem to work, and the GPIOs always read LOW. My setup has been tested twice in Raspberry Pi OS (the resistors worked there, measured with a scope). gpiozero uses rpi.gpio as the pin factory. A different pin was tested too.

UPDATE: The pip3 version of RPi.GPIO (and gpiozero) works fine.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: python3-rpi.gpio 0.6.5-1ubuntu3
ProcVersionSignature: Ubuntu 5.4.0-1021.24-raspi 5.4.65
Uname: Linux 5.4.0-1021-raspi aarch64
ApportVersion: 2.20.11-0ubuntu27.9
Architecture: arm64
CasperMD5CheckResult: skip
Date: Wed Oct 14 20:27:59 2020
ImageMediaBuild: 20200731
ProcEnviron:
 TERM=alacritty
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=C.UTF-8
 SHELL=/bin/bash
SourcePackage: rpi.gpio
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.