CR3 RAW files are disabled in third-party document pickers when accessed through Nextcloud File Provider

Canon .CR3 RAW files exposed through the Nextcloud iOS File Provider cannot be selected in Photomator’s document picker.

The same CR3 files work correctly in Photomator when stored locally under On My iPhone.

Nextcloud itself can display previews for these CR3 files correctly.

This appears to be related specifically to how CR3 files are exposed to third-party applications through the Nextcloud File Provider.

Steps to reproduce

1. Store a Canon .CR3 RAW file in Nextcloud.
2. Open Nextcloud on iOS and make sure the file is fully downloaded / available offline.
3. Open Photomator.
4. Use Photomator’s file browser to navigate to the Nextcloud location through the iOS document picker.
5. Navigate to the folder containing the CR3 files.

Actual behavior

The .CR3 files are visible and their filename, size and date are shown, but they are greyed out and cannot be selected.

Downloading the files beforehand / making them available offline does not change the behavior.

Expected behavior

CR3 files should be selectable by applications that support the format.

Photomator supports these exact CR3 files when they are stored locally on the iPhone.

Comparison / verification

I tested the same workflow outside the Nextcloud File Provider:

1. Copy a CR3 file to On My iPhone.
2. Open Photomator.
3. Browse to the local file.

The CR3 file is immediately selectable, a thumbnail is displayed, and Photomator can open and edit it normally.

Therefore:

• CR3 stored locally → Photomator: works
• CR3 through Nextcloud File Provider → Photomator: disabled
• CR3 through Nextcloud File Provider after downloading it locally/offline → Photomator: still disabled

This suggests that the issue is not RAW/CR3 support in Photomator or iOS itself, but may be related to the metadata/content type or capabilities exposed by the Nextcloud File Provider for CR3 files.

Additional information

• File format: Canon CR3 RAW (.CR3)
• Camera: Canon EOS R8
• File size in tested examples: approximately 33–34 MB
• Nextcloud can generate/display previews for these files correctly.
• The files themselves are valid and can be opened by Photomator when copied outside the Nextcloud File Provider.
• Other supported image formats such as JPEG can be selected normally through the Nextcloud File Provider.

Local storage

A CR3 file stored under On My iPhone is recognized by Photomator, displays a thumbnail, and can be selected normally.

No files or tests are named. Start by reproducing the CR3 selection failure through the iOS File Provider with Photomator, then compare the metadata or content type exposed for CR3 and JPEG files; done means supported CR3 files are selectable through the provider.