Make sure that you have about:blank installed on your iOS device to manage your rules.
Have iCloud enabled
Activate the "Start at login" option to let about:blank synchronize the blocked URLs.
Go to the top menu bar & click on Safari.
Select 'Preferences...' in the dropdown.
A new window should appear now. Click on 'Extensions' in the top bar of that window.
You should see about:blank on the left side now of the window now. Check the checkbox to activate about:blank.