Screen mirror with Samsung TV

• Verify that your model Samsung TV is AirPlay-enabled, i.e. that it can receive AirPlay streams. List of AirPlay-enabled smart TVs and third party streaming devices - Apple
• Verify that you have activated Apple AirPlay in your TV settings. How to stream from an iPhone using AirPlay 2 - Samsung Support

From what device are you trying to stream?

Is the TV already turned on when you try to start the AirPlay stream?

If your Samsung TV isn't appearing in the screen mirroring options, ensure both devices are on the same Wi-Fi network, restart them, and check that screen mirroring is enabled in the TV's settings. Also, try updating the firmware and using the SmartThings app.

As an alternative, you can use the Docast app for reliable screen mirroring