On iOS v15.4, both the iPhone and iPad, Legend 6.0.5 (current release at the moment), creation of mirrors and links does not seem to work.
On a new item, typing (( or [[ causes the iOS keyboard to disappear, leaving you with a full screen of your list, no way to type. After that, clicking on the item after the (( or [[ brings up the keyboard, which promptly disappears with the first character you type.
Expected it to allow me to continue to type after the (( or [[, the present me with potential matching items for linking or mirroring…?