Comment 2 for bug 1949615

This python program shows the problem

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#!/usr/bin/python3
# -*- coding: utf-8 -*-
#
from pydbus import SessionBus
from time import sleep

##### Global constants
#
item = "org.freedesktop.Notifications"
path = "/org/freedesktop/Notifications"
interface = "org.freedesktop.Notifications"
app_name = "NotifyTest"
icon = "/usr/share/icons/breeze/devices/64/camera-web.svg"
actions_list = []
hint = {}

bus = SessionBus()
notifications = bus.get('.Notifications')

##### Global variables
#
our_notify_id = 0
timeout = 3000 # ms
wait4 = 0 # s
body = "from NotifyTest.py"

while wait4 < 6:
    wait4 += 1
    message = "The next wait will be %ss" % wait4

# This should replace any previous notification still there...
# (can do this with notify-send command, but doing it in python allows
# us to use a fixed id for replacement).
#
    our_notify_id = notifications.Notify(app_name, our_notify_id, icon,
       message, body, actions_list, hint, timeout)
    print("our_notify_id:", our_notify_id)

# At Ubuntu 21.10 we have to change this to get the new message seen...
#
# our_notify_id += 1
    print(message)

    sleep(wait4)

print("Done")
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On 21.04 after the sleep exceeds the 3s timeout a new info message box is displayed.

On 21.10 after the sleep exceeds the 3s timeout nothing is shown.