Same here, this is the situation:
Safari click on file (es. mail attachment):
IOS 12: straight to open file screen
IOS 13: downloads the file somewhere, interface is not clear, but when you figure out and find where to click you proceed to open file screen
Safari open file:
IOS 12: display screen with my custom UTI Type name and "open file with MyApp" button, on click opens the app correctly
IOS 13: display screen with the description of my custom UTI Type name, no buttons, look like it's broken. Need to look at the top for the share icon
Share dialog:
IOS 12: no problem
IOS 13: need to add (that i already had), i have a custom file, so no concurrent apps
<key>UTTypeConformsTo</key>
<array>
<string>public.data</string>
</array>
On "Copy to MyApp" click
IOS 12: Opens app at the proper screen with file loaded
IOS 13: Safari crashes, doesn't open the app, scroll to the frist ios screen
Looks like a fail on every side, how can this have been missed? or is there a documentation to apply the proper fixes?
The UX on IOS13 (even if it worked) is a 10 years step back in user experience on the import flow, i hope it's not intended.