Hello,
iPhone 12, iOS 14.3, no jailbreak
I tried installing Delta Emulator and UTM Emulator using the custom IPA sideload feature in App+. The apps install and open, but when importing anything from the apps' built in file picker, or when sharing from the Files app, nothing happens. I can see the file that should be imported, it is not grayed out, but clicking on it does nothing. After some research I stumbled upon this issue in UTM's issue tracker: Cannot import iso drive image. In the replies, there are a couple of potential fixes, all suggesting that the problem is in the way the apps are signed. One of the last replies is a PR for another signer app with the description:
Could you please take a look at this? It renders these apps completely unusable.
Thanks
EDIT: I tried installing both apps with AltStore and a free developer license and the file browser/import works on both that way. This means that it is definitely an issue with App+.