Save to Files from Mail app does not work

[bytersproblem]

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Describe the bug

When I try to save mail attachments with "Save to Files" from Mail app, nothing happens

Context

• Hardware: AMD Ryzen 3 with 32 GB of RAM
• YunoHost version: 11.2.11.3
• I have access to my server: through ssh
• Are you in a special context or did you perform some particular tweaking on your YunoHost instance?: I installed sslh to share port 443 betweeen https and openvpn, changed the port in conf.d/nginx.domain.conf to 444
• Using, or trying to install package version/branch:
• If upgrading, current package version: 28.0.5~ynh1

Steps to reproduce

1. Install and open Mail app
2. Register imap account (Gmail) with app password
3. filnd the mail with attachments
4. try to save the attachment as Save to Files

Expected behavior

Dialog opens and I save the files to some folder on the Nextcloud server

Logs

Nothing concerning the mail app shows in the logs. This dialog appears, e.g., in files app when I try to move or copy files to another location