I found another issue now. When saving new documents in iCloud (within StreamByter), they are not seen on other devices in iOS. On Mac everything works, at least in Mojave. I can see also newly created files from iOS. That means, iCloud sync is not completely broken – files can be stored but not recalled. I hope that you are healthy and have time to solve the issues.
My iPad Mini2 - iOS 12.5.3, can see all iCloud files created on all devices. But my iPhones (iOS 14.6) only see their own files created locally and saved to iCloud. iOS devices have a local folder called StreamByter but there isn't one on the iCloud Drive - is that the problem?