In my opinion there are very few trusted open-source BTC wallets and unfortunately there are no one for iOS. I mean I can’t trust most BTC wallets on the App Store for different reasons. Some of them were made by weird companies and others are not open-source.
There are fewer Bitcoin wallets for iOS than on Android.
One of the open-source Bitcoin wallets for iOS that I trust at the moment is BlueWallet.
Electrum developers are more active on Github than on the Bitcointalk forum. Try to create a topic and submit it here:
https://github.com/spesmilo/electrum/pulls.