[Bug]: "Add to your Nextcloud" not working for shared *.md files

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

When someone shares a Markdown file as a link, I cannot add it to my Nextcloud with the "Add to your Nextcloud" button.

Steps to reproduce

1. alice@example.com creates a Markdown file
2. alice@example.com does Sharing -> "Share Link"
3. alice@example.com shares the link with Bob
4. bob@example.com clicks opens the link. Notice that because it is a Markdown file, Nextcloud Text loads.
5. bob@example.com clicks on "Add to your Nextcloud"
6. bob@example.com enters his cloud address (bob@example.com)
7. Bob tries to click Enter or the Arrow button

Actual behaviour

Nothing happens.

Notice that for other files, such as images, add-to-your-nextcloud works. But for Markdown files opening in Text, it doesn't.

Expected behavior

The federated sharing flow should run through.

Installation method

Community Docker image

Nextcloud Server version

28

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.2

Web server

Apache (supported)

Database engine version

MariaDB

Is this bug present after an update or on a fresh install?

Updated from a MINOR version (ex. 22.1 to 22.2)

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

{
    "system": {
        "htaccess.RewriteBase": "\/",
        "memcache.local": "\\OC\\Memcache\\APCu",
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "port": 6379,
            "timeout": 0,
            "password": "***REMOVED SENSITIVE VALUE***"
        },
        "filelocking.enabled": true,
        "apps_paths": [
            {
                "path": "\/var\/www\/html\/apps",
                "url": "\/apps",
                "writable": false
            },
            {
                "path": "\/var\/www\/html\/custom_apps",
                "url": "\/custom_apps",
                "writable": true
            }
        ],
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "cloud.example.com"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "overwrite.cli.url": "https:\/\/cloud.example.com",
        "dbtype": "mysql",
        "version": "28.0.2.5",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "trusted_proxies": "***REMOVED SENSITIVE VALUE***",
        "forwarded_for_headers": [
            "HTTP_X_FORWARDED_FOR"
        ],
        "overwritehost": "cloud.example.com",
        "overwriteprotocol": "https",
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "loglevel": 0,
        "maintenance": false,
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpmode": "smtp",
        "mail_sendmailmode": "smtp",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpauth": 1,
        "mail_smtpauthtype": "PLAIN",
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "587",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpsecure": "tls",
        "forcessl": true,
        "default_phone_region": "DE",
        "theme": "",
        "app_install_overwrite": [
            "whiteboard",
            "twofactor_nextcloud_notification",
            "suspicious_login",
            "qownnotesapi",
            "quota_warning",
            "twofactor_admin",
            "groupfolders"
        ],
        "enable_previews": true,
        "enabledPreviewProviders": [
            "OC\\Preview\\BMP",
            "OC\\Preview\\GIF",
            "OC\\Preview\\JPEG",
            "OC\\Preview\\Krita",
            "OC\\Preview\\MarkDown",
            "OC\\Preview\\MP3",
            "OC\\Preview\\OpenDocument",
            "OC\\Preview\\PNG",
            "OC\\Preview\\TXT",
            "OC\\Preview\\XBitmap",
            "OC\\Preview\\Movie",
            "OC\\Preview\\HEIC"
        ]
    }
}

List of activated Apps

Enabled:
  - activity: 2.20.0
  - admin_audit: 1.18.0
  - bruteforcesettings: 2.8.0
  - cloud_federation_api: 1.11.0
  - comments: 1.18.0
  - contactsinteraction: 1.9.0
  - cospend: 1.6.0
  - dav: 1.29.1
  - deck: 1.12.1
  - federatedfilesharing: 1.18.0
  - federation: 1.18.0
  - files: 2.0.0
  - files_pdfviewer: 2.9.0
  - files_reminders: 1.1.0
  - files_sharing: 1.20.0
  - files_trashbin: 1.18.0
  - files_versions: 1.21.0
  - firstrunwizard: 2.17.0
  - forms: 4.1.0
  - logreader: 2.13.0
  - lookup_server_connector: 1.16.0
  - nextcloud_announcements: 1.17.0
  - notes: 4.9.2
  - notifications: 2.16.0
  - notify_push: 0.6.9
  - oauth2: 1.16.3
  - password_policy: 1.18.0
  - photos: 2.4.0
  - polls: 6.0.1
  - previewgenerator: 5.4.0
  - privacy: 1.12.0
  - provisioning_api: 1.18.0
  - qownnotesapi: 23.12.0
  - quota_warning: 1.18.0
  - recognize: 6.0.1
  - recommendations: 2.0.0
  - related_resources: 1.3.0
  - richdocuments: 8.3.1
  - richdocumentscode: 23.5.705
  - serverinfo: 1.18.0
  - settings: 1.10.1
  - sharebymail: 1.18.0
  - support: 1.11.0
  - survey_client: 1.16.0
  - suspicious_login: 6.0.0
  - systemtags: 1.18.0
  - text: 3.9.1
  - theming: 2.3.0
  - translate: 2.0.0
  - twofactor_admin: 4.4.0
  - twofactor_backupcodes: 1.17.0
  - twofactor_nextcloud_notification: 3.8.0
  - twofactor_totp: 10.0.0-beta.2
  - twofactor_webauthn: 1.3.2
  - updatenotification: 1.18.0
  - user_status: 1.8.1
  - viewer: 2.2.0
  - weather_status: 1.8.0
  - workflowengine: 2.10.0
Disabled:
  - circles: 28.0.0-dev (installed 28.0.0-dev)
  - dashboard: 7.8.0 (installed 7.0.0)
  - encryption: 2.16.0
  - files_external: 1.20.0
  - files_rightclick: 0.15.1 (installed 1.6.0)
  - groupfolders: 16.0.3 (installed 16.0.3)
  - integration_deepl: 1.1.2 (installed 1.1.2)
  - user_ldap: 1.19.0

Nextcloud Signing status

No errors have been found.

Nextcloud Logs

n/a

Additional info

n/a

Start by reproducing the shared Markdown-link flow in the Nextcloud Text app: open a shared .md file, click “Add to your Nextcloud,” and submit the cloud address with Enter and the arrow button. Compare this with the working flow for an image and trace where the Text-specific flow stops. Done means federated sharing completes for shared Markdown files as it does for other files.