iOS 9 App does not suggest apps to open unknown files

For at least a year I can not open files like .cbz or .epub on the old iPad that can’t be updated further than iOS 9.3.6.
The file can be downloaded but it does not suggest any Reader-App like it did before. Therefore I have no chance of opening the file in any other way.

It still works for files like .pdf, where it suggests all the reading apps I have installed.

Is this an iOS issue or a Seafile issue?
A solution would be very appreciated!

I guess no one is using an older iPad anymore? :frowning: