Hi, you can stop the pop up using a simple 3 step process that I've provided below.

1) Go to Menu >> System >> Setup >> navigate to Smart Hub Terms & conditions page section.

2) On Smart Hub Terms & conditions page scroll down and uncheck the Sync plus and Marketing option, then complete the rest of the setup process.

3) After the Setup is complete, unplug the tv from the wall for 30secs and re-plug the TV to stop the adds related to Sync plus.