On Galaxy devices, the screen mirroring feature is called Smart View. Smart View is not an app but a settings feature. You can find it by pulling down twice on your screen, and you may have to swipe to the left to see the icon. Tap that and then select your Samsung TV from the list of available devices.

Swipe down from the top of the screen to open the Quick Select panel, then find and tap on the SmartView icon. I had to swipe down from the top of the screen twice due to an abundance of notifications, so if you don't see it then try that. As you can see on my Galaxy Z Fold 5, it is in the bottom left-hand corner.

Navigate to the Quick Settings tray on your device by swiping down from the top. Tap the three-dot menu on the top-right of your home screen. To add the Cast icon to the tray, select Edit buttons. You can view the Cast icon in the list. Long press and drag the icon into the tray. Tap Done at the bottom of the screen to save your settings.