PyQt5 bubble notification, original code from https://stackoverflow.com/a/59327658/8201723 (adapted for latest PyQt5 version)

bubble_notification.py

import sys
from PyQt5.QtCore import (QRectF, Qt, QPropertyAnimation, pyqtProperty, 
                          QPoint, QParallelAnimationGroup, QEasingCurve)
from PyQt5.QtGui import QPainter, QPainterPath, QColor, QPen
from PyQt5.QtWidgets import (QLabel, QWidget, QVBoxLayout, QApplication,
                             QLineEdit, QPushButton)


class BubbleLabel(QWidget):

    BackgroundColor = QColor(195, 195, 195)
    BorderColor = QColor(150, 150, 150)

    def __init__(self, *args, **kwargs):
        self.animationGroup = None

        text = kwargs.pop("text", "")
        super(BubbleLabel, self).__init__(*args, **kwargs)
        self.setWindowFlags(
            Qt.Window | Qt.Tool | Qt.FramelessWindowHint | 
            Qt.WindowStaysOnTopHint | Qt.X11BypassWindowManagerHint)
        # Set minimum width and height
        self.setMinimumWidth(200)
        self.setMinimumHeight(58)
        self.setAttribute(Qt.WA_TranslucentBackground, True)
        layout = QVBoxLayout(self)
        # Top left and bottom right margins (16 below because triangles are included)
        layout.setContentsMargins(8, 8, 8, 16)
        self.label = QLabel(self)
        layout.addWidget(self.label)
        self.setText(text)
        # Get screen height and width
        self._desktop = QApplication.instance().desktop()

    def setText(self, text):
        self.label.setText(text)

    def text(self):
        return self.label.text()

    def stop(self):
        self.hide()
        self.animationGroup.stop()
        self.close()

    def show(self):
        super(BubbleLabel, self).show()
        # Window start position
        startPos = QPoint(
            self._desktop.screenGeometry().width() - self.width() - 50,
            self._desktop.availableGeometry().height() - self.height())
        endPos = QPoint(
            self._desktop.screenGeometry().width() - self.width() - 50,
            self._desktop.availableGeometry().height() - self.height() * 3 - 5)
        self.move(startPos)
        # Initialization animation
        self.initAnimation(startPos, endPos)

    def initAnimation(self, startPos, endPos):
        # Transparency animation
        opacityAnimation = QPropertyAnimation(self, b"opacity")
        opacityAnimation.setStartValue(1.0)
        opacityAnimation.setEndValue(0.0)
        # Set the animation curve
        opacityAnimation.setEasingCurve(QEasingCurve.InQuad)
        opacityAnimation.setDuration(4000)  
        # Moving up animation
        moveAnimation = QPropertyAnimation(self, b"pos")
        moveAnimation.setStartValue(startPos)
        moveAnimation.setEndValue(endPos)
        moveAnimation.setEasingCurve(QEasingCurve.InQuad)
        moveAnimation.setDuration(5000)  
        # Parallel animation group (the purpose is to make the two animations above simultaneously)
        self.animationGroup = QParallelAnimationGroup(self)
        self.animationGroup.addAnimation(opacityAnimation)
        self.animationGroup.addAnimation(moveAnimation)
        # Close window at the end of the animation
        self.animationGroup.finished.connect(self._close)
        self.animationGroup.start()

    def _close(self):
        self.close()

    def paintEvent(self, event):
        super(BubbleLabel, self).paintEvent(event)
        painter = QPainter(self)
        painter.setRenderHint(QPainter.Antialiasing)  # Antialiasing

        rectPath = QPainterPath()                     # Rounded Rectangle
        triPath = QPainterPath()                      # Bottom triangle

        height = self.height() - 8                    # Offset up 8
        rectPath.addRoundedRect(QRectF(0, 0, self.width(), height), 5, 5)
        x = self.width() - 20  # tripath crest 20px left from the farthest right end of the widget
        triPath.moveTo(x - 10, height)                     # Move to the bottom horizontal line 4/5
        # Draw triangle
        triPath.lineTo(x + 6, height + 8)
        triPath.lineTo(x + 12, height)

        rectPath.addPath(triPath)                     # Add a triangle to the previous rectangle

        # Border brush
        painter.setPen(QPen(self.BorderColor, 1, Qt.SolidLine,
                            Qt.RoundCap, Qt.RoundJoin))
        # Background brush
        painter.setBrush(self.BackgroundColor)
        # Draw shape
        painter.drawPath(rectPath)
        # Draw a line on the bottom of the triangle to ensure the same color as the background
        painter.setPen(QPen(self.BackgroundColor, 1,
                            Qt.SolidLine, Qt.RoundCap, Qt.RoundJoin))
        painter.drawLine(x, height, x + 12, height)

    def windowOpacity(self):
        return super(BubbleLabel, self).windowOpacity()

    def setWindowOpacity(self, opacity):
        super(BubbleLabel, self).setWindowOpacity(opacity)

    # Since the opacity property is not in QWidget, you need to redefine one
    opacity = pyqtProperty(float, windowOpacity, setWindowOpacity)


class TestWidget(QWidget):

    def __init__(self, *args, **kwargs):
        super(TestWidget, self).__init__(*args, **kwargs)
        layout = QVBoxLayout(self)
        self.msgEdit = QLineEdit(self)
        self.msgEdit.returnPressed.connect(self.onMsgShow)
        self.msgButton = QPushButton("Display content", self)
        self.msgButton.clicked.connect(self.onMsgShow)
        layout.addWidget(self.msgEdit)
        layout.addWidget(self.msgButton)

    def onMsgShow(self):
        msg = self.msgEdit.text().strip()
        if not msg:
            return
        if hasattr(self, "_blabel"):
            self._blabel.stop()
            self._blabel.deleteLater()
            del self._blabel
        self._blabel = BubbleLabel()
        self._blabel.setText(msg)
        self._blabel.show()


if __name__ == "__main__":
    app = QApplication(sys.argv)
    w = TestWidget()
    w.show()
    sys.exit(app.exec_())