allowedUtiTypes property
You need to register the document types that your application can open with iOS. To do this you need to add a document type to your app’s Info.plist for each document type that your app can open. Additionally if any of the document types are not known by iOS, you will need to provide an Uniform Type Identifier (UTI) for that document type.
More info: https://developer.apple.com/library/archive/qa/qa1587/_index.html
Implementation
final List<String>? allowedUtiTypes;