Окно создается, но открыть его нельзя

НИКОГДА НЕ ИЗМЕНЯЙТЕ код, сгенерированный Qt Designer, НИКОГДА.
Создайте другой класс, который наследуется от соответствующего виджета, и используйте созданный класс для его заполнения.

windowOpacity : double

Это свойство содержит уровень непрозрачности окна.
Допустимый диапазон непрозрачности — от 1,0 (полностью непрозрачный) до 0,0 (полностью прозрачный).
По умолчанию значение этого свойства равно 1,0.

'''
from PyQt6 import QtCore, QtGui, QtWidgets
'''
from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):

#?        super(Ui_MainWindow, self).__init__()    

        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(800, 600)
        
#?        MainWindow.setWindowOpacity(0.0)

        MainWindow.setStyleSheet("background-color: rgb(89, 89, 89);")
        MainWindow.setIconSize(QtCore.QSize(32, 32))
        self.centralwidget = QtWidgets.QWidget(parent=MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.scrollArea = QtWidgets.QScrollArea(parent=self.centralwidget)
        self.scrollArea.setGeometry(QtCore.QRect(50, 20, 161, 545))
        self.scrollArea.setWidgetResizable(True)
        self.scrollArea.setObjectName("scrollArea")
        self.scrollAreaWidgetContents = QtWidgets.QWidget()
        self.scrollAreaWidgetContents.setGeometry(QtCore.QRect(0, 0, 159, 543))
        self.scrollAreaWidgetContents.setObjectName("scrollAreaWidgetContents")
        self.label = QtWidgets.QLabel(parent=self.scrollAreaWidgetContents)
        self.label.setGeometry(QtCore.QRect(10, 20, 141, 16))
        self.label.setStyleSheet("color: rgb(255, 255, 255);")
        self.label.setObjectName("label")
        self.label_2 = QtWidgets.QLabel(parent=self.scrollAreaWidgetContents)
        self.label_2.setGeometry(QtCore.QRect(10, 40, 141, 16))
        self.label_2.setStyleSheet("color: rgb(255, 255, 255);")
        self.label_2.setObjectName("label_2")
        self.verticalScrollBar = QtWidgets.QScrollBar(parent=self.scrollAreaWidgetContents)
        self.verticalScrollBar.setGeometry(QtCore.QRect(144, 0, 15, 482))
        self.verticalScrollBar.setMaximum(1200)
        self.verticalScrollBar.setOrientation(QtCore.Qt.Orientation.Vertical)
        self.verticalScrollBar.setObjectName("verticalScrollBar")
        self.scrollArea.setWidget(self.scrollAreaWidgetContents)
        self.Settings = QtWidgets.QToolButton(parent=self.centralwidget)
        self.Settings.setGeometry(QtCore.QRect(10, 20, 32, 32))
        icon = QtGui.QIcon()
        icon.addPixmap(QtGui.QPixmap("copy_4043715.png"), QtGui.QIcon.Mode.Normal, QtGui.QIcon.State.Off)
        self.Settings.setIcon(icon)
        self.Settings.setIconSize(QtCore.QSize(64, 64))
        self.Settings.setAutoRaise(True)
        self.Settings.setObjectName("Settings")
        self.Settings_2 = QtWidgets.QToolButton(parent=self.centralwidget)
        self.Settings_2.setGeometry(QtCore.QRect(10, 60, 32, 32))
        icon1 = QtGui.QIcon()
        icon1.addPixmap(QtGui.QPixmap("search_4232773.png"), QtGui.QIcon.Mode.Normal, QtGui.QIcon.State.Off)
        self.Settings_2.setIcon(icon1)
        self.Settings_2.setIconSize(QtCore.QSize(64, 64))
        self.Settings_2.setAutoRaise(True)
        self.Settings_2.setObjectName("Settings_2")
        self.Settings_3 = QtWidgets.QToolButton(parent=self.centralwidget)
        self.Settings_3.setGeometry(QtCore.QRect(10, 100, 32, 32))
        icon2 = QtGui.QIcon()
        icon2.addPixmap(QtGui.QPixmap("settings_4502134.png"), QtGui.QIcon.Mode.Normal, QtGui.QIcon.State.Off)
        self.Settings_3.setIcon(icon2)
        self.Settings_3.setIconSize(QtCore.QSize(64, 64))
        self.Settings_3.setAutoRaise(True)
        self.Settings_3.setObjectName("Settings_3")
        self.textEdit = QtWidgets.QTextEdit(parent=self.centralwidget)
        self.textEdit.setGeometry(QtCore.QRect(210, 20, 590, 540))
        font = QtGui.QFont()
        font.setFamily("Dubai")
        font.setPointSize(16)
        self.textEdit.setFont(font)
        self.textEdit.setStyleSheet("color: rgb(213, 213, 213);")
        self.textEdit.setObjectName("textEdit")
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(parent=MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 22))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(parent=MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "Saturn"))
        self.label.setText(_translate("MainWindow", "File1.txt"))
        self.label_2.setText(_translate("MainWindow", "File2.txt"))
        self.Settings.setText(_translate("MainWindow", "..."))
        self.Settings_2.setText(_translate("MainWindow", "..."))
        self.Settings_3.setText(_translate("MainWindow", "..."))
        self.textEdit.setHtml(_translate("MainWindow", "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0//EN\" \"http://www.w3.org/TR/REC-html40/strict.dtd\">\n"
"<html><head><meta name=\"qrichtext\" content=\"1\" /><style type=\"text/css\">\n"
"p, li { white-space: pre-wrap; }\n"
"</style></head><body style=\" font-family:\'Dubai\'; font-size:16pt; font-weight:400; font-style:normal;\">\n"
"<p style=\" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;\"><span style=\" font-family:\'MS Shell Dlg 2\'; font-size:7.875pt;\">1232131</span></p>\n"
"<p style=\"-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; font-family:\'MS Shell Dlg 2\'; font-size:7.875pt;\"><br /></p></body></html>"))


class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self):
        super().__init__()
        self.setupUi(self) 

        # тут ваша логика
        

if __name__ == "__main__":
    import sys
    
    app = QtWidgets.QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec())