We apologize for this mishap, I should have set the "Min iOS version" for our v13.0.30 release to "iOS 13+", and then those with these older devices simply would NOT have seen the update. The downside would have been, is that if you ever removed the app or had to do "App Restore (e.g. from Cloud)" - then you'd not get the app back.
Our intended solution to this is already being implemented, which is to create a NEW product called "iFly EFB - LEGACY" which will also be available on the App Store -- instructing users to ONLY install it if they are on iOS 12 or lower. Then we'll redirect our users with old iPads to that application to keep them running. To our knowledge, there are about 100 of these devices with iFly EFB on them now.
This new Legacy App, as of tonight, has been submitted to Apple for Test Flight deployment, as well as for AppStore deployment. As soon as we hear from a few beta testers that the Legacy App appears to be working, we'll release it on the AppStore -- which may be as soon as mid-next-week (April 3rd), but that's only if there aren't any hiccups.