Install the tvOS profile hopefully that should get rid of it
Nothing negative I used it on my iPad to stop it updating from 12.1.1 before the jailbreak was releasedDoes this work if you are not jailbroken? I am waiting for the A12 JB and the pop up is driving me nuts. would I install the tvOS profile and delete the iOS profile? And are there any negative effects to doing that?
Check to see if in your settings you have apps to automatically update. Turn it off and manually update your apps thru the App Store. Make sure that the tvOS beta 12 is properly installed and trusted. Look at your iPhone storage to delete any iOS update downloads. Shut off your phone and re-start it and you should be good to go. One other thing you might want to try is to sign out of iCloud completely, shutdown, restart, and log back in.
P.S. - This is BEFORE you jailbreak.
Been there, done that.