Can a VPN Killswitch be configured/programmed in iOS?
Check out this thread.
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
let myEmail = "eskimo" + "1" + "@apple.com"
Unfortunately VPN Killswitch is NOT currently supported on iOS. While isOnDemandEnabled is reestablishing a VPN connection, Internet traffic is inhibited to some degree but not entirely, so does not protect against IP leaks.
Perhaps consider raising an enhancement request to help Apple gauge its importance to the VPN community.