Files in folders marked as available offline are not re-downloaded after iOS backup/restore on a new device

Summary

I just switched from one iPhone to another, and the files in folders I had marked as available offline in the Nextcloud app were not re-downloaded on the second iPhone after the restore from iCloud backup of the first iPhone.

Steps to reproduce

1. Setup Nextcloud on first iOS device
2. Mark some folders as available offline and wait for all the files within to be fully downloaded
3. Backup first iOS device to iCloud
4. Shut down first iOS device
5. Set first iOS device aside and get the second iOS device
6. Turn on second iOS device
7. Setup second iOS device by restoring iCloud backup from first iOS device
8. Wait for all data and apps to be restored
9. Open Nextcloud app on second iOS device
10. Authenticate again with same Nextcloud account
11. Wait for files in folders marked as available offline to be downloaded

Expected behaviour

At step number 11, I expect every file in the folders marked as available offline to be downloaded on the second iOS device.

Actual behaviour

At step number 11, those files don't get downloaded. Only newly added files in these folders get automatically downloaded on the second iOS device, but there's no way to get the Nextcloud app to re-download files on this second iOS device that had been previously downloaded on the first iOS device. I actually tried to disable the mark as available offline bit for those folders, and re-enable it, with no luck.

The only way I could get the Nextcloud app to work as expected on the second iOS device was to delete it, thus agreeing to delete all the app data; only to download it again and start over manually.

Reasoning or why should it be changed/implemented?

Users expect to be able to setup new iOS devices from iCloud backups of old iOS devices, especially when they get a new device.

Users should also be able to rely on the feature for marking folders as available offline to work as expected, even across backup/restore cycles.

iOS version

iOS 14.1 GM Seed (18A8395).

App version

Nextcloud Coherence for iOS 3.0.8.0

Server configuration

Operating system:

FreeBSD 12.1-RELEASE-p10

Web server:

nginx 1.18.0_25,2

Configured to use php-fpm.

Database:

postgresql12-server-12.4_1

PHP version:

php73-7.3.23

Nextcloud version: (see Nextcloud admin page)

19.0.3

No source files or tests are named in the report. Start by reproducing the iCloud backup/restore flow on iOS and trace how folders marked available offline are handled after re-authentication; the issue is done when all previously downloaded folder files are downloaded again on the restored device.