[Bug]: Sharing Calendar not possible due to empty contact list in "Share with users or groups" pulldown list

⚠️ Before submitting, please verify the following: ⚠️

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

Bug description

The share dialog is looking incomplete.
...
No contacts appear in the pulldown list. However there are other users registered in nextcloud.

Steps to reproduce

1. open Calendar
2. click on the pencil
3. try to share calendar

Expected behavior

When clicking on the share dialog, share by e-mail should be an option.
...
Other users appear in the list an I can share my calendar

Which files are affected by this bug

No files

Operating system

Windows

Which version of the operating system you are running.

Ubuntu Server 24.04 1 LTS - Linux 6.8.0-49-generic x86_64

Package

Official Linux AppImage

Nextcloud Server version

Nextcloud Hub 9 (30.0.2)

Nextcloud Desktop Client version

?

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

Fresh desktop client install

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

Are you using an external user-backend?

• Default internal user-backend
• LDAP/ Active Directory
• SSO - SAML
• Other

Nextcloud Server logs

Additional info

No response

Start at the Calendar share dialog by opening Calendar, clicking the pencil, and trying to share a calendar; reproduce the empty contact list with the stated Nextcloud versions. Trace the dialog's user lookup behavior and verify that existing users and email sharing appear as expected.