[Bug]: Calendar Appointments: unable to select "Additional calendars to check for conflicts"

⚠️ This issue respects the following points: ⚠️

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

Bug description

When making a calendar appointment, you have an option to select, from a drop-down menu, "Additional calendars to check for conflicts". However, even though I have many other calendars that I have access to, this drop-down menu doesn't activate, so I am unable to pick other calendars to include, resulting in appointments being scheduled at times that conflict with the other calendars.

Steps to reproduce

Open the calendar app, make sure you have multiple calendars configured
On the lower left, in the Appointments area, click the + to "Add new"
In the Appointment configuration dialog box notice the "Additional calendars to check for conflicts" - you will not be able to open this drop-down to select other calendars.

Expected behavior

I should be able to select any of the calendars that I have access to so that the calendar appointment will take those into consideration when making appointment times available.

Nextcloud Server version

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.3

Web server

Nginx

Database engine version

MariaDB

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

None

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

[x] Default user-backend (database)
[ ] LDAP/ Active Directory
[ ] SSO - SAML
[ ] Other

Configuration report

{ "system": { "instanceid": "REMOVED SENSITIVE VALUE", "passwordsalt": "REMOVED SENSITIVE VALUE", "secret": "REMOVED SENSITIVE VALUE", "trusted_domains": [ "nc.REMOVED SENSITIVE VALUE.net", ], "enable_previews": true, "preview_max_x": 1024, "preview_max_y": 768, "preview_max_scale_factor": 1, "enabledPreviewProviders": [ "OC\Preview\PNG", "OC\Preview\JPEG", "OC\Preview\GIF", "OC\Preview\BMP", "OC\Preview\XBitmap", "OC\Preview\Movie", "OC\Preview\PDF", "OC\Preview\MP3", "OC\Preview\TXT", "OC\Preview\MarkDown" ], "filesystem_check_changes": 0, "activity_expire_days": 14, "knowledgebaseenabled": false, "default_phone_region": "US", "auth.bruteforce.protection.enabled": true, "blacklisted_files": [ ".htaccess", "Thumbs.db", "thumbs.db" ], "cronlog": true, "datadirectory": "REMOVED SENSITIVE VALUE", "overwrite.cli.url": "https://nc.REMOVED SENSITIVE VALUE.net/nextcloud", "htaccess.RewriteBase": "/nextcloud", "dbtype": "mysql", "version": "30.0.0.14", "dbname": "REMOVED SENSITIVE VALUE", "dbhost": "REMOVED SENSITIVE VALUE", "dbport": "", "dbtableprefix": "oc", "mysql.utf8mb4": true, "dbuser": "REMOVED SENSITIVE VALUE", "dbpassword": "REMOVED SENSITIVE VALUE", "installed": true, "memcache.local": "\OC\Memcache\APCu", "memcache.locking": "\OC\Memcache\Redis", "memcache.distributed": "\OC\Memcache\Redis", "filelocking.enabled": "true", "redis": { "host": "REMOVED SENSITIVE VALUE", "port": 0, "dbindex": 0, "timeout": 1.5 }, "log_type": "file", "logfile": "/srv/nextcloud_data/nextcloud.log", "loglevel": 1, "log_rotate_size": 104857600, "share_folder": "/Incoming", "skeletondirectory": "", "templatedirectory": "", "theme": "", "trashbin_retention_obligation": "auto, 7", "updater.release.channel": "stable", "twofactor_enforced": "false", "twofactor_enforced_groups": [], "twofactor_enforced_excluded_groups": [], "mail_smtpdebug": true, "mail_smtpmode": "smtp", "mail_smtpsecure": "ssl", "mail_sendmailmode": "smtp", "mail_from_address": "REMOVED SENSITIVE VALUE", "mail_domain": "REMOVED SENSITIVE VALUE", "mail_smtpauthtype": "PLAIN", "mail_smtpauth": 1, "mail_smtphost": "REMOVED SENSITIVE VALUE", "mail_smtpport": "465", "mail_smtpname": "REMOVED SENSITIVE VALUE", "mail_smtppassword": "REMOVED SENSITIVE VALUE", "app_install_overwrite": [ "twofactor_totp", "onlyoffice" ], "maintenance": false, "config_is_read_only": true } }

List of activated Apps

Enabled:

activity: 3.0.0
calendar: 5.0.1
circles: 30.0.0-dev
cloud_federation_api: 1.13.0
comments: 1.20.1
contacts: 6.1.0
contactsinteraction: 1.11.0
dashboard: 7.10.0
dav: 1.31.1
federatedfilesharing: 1.20.0
federation: 1.20.0
files: 2.2.0
files_downloadlimit: 3.0.0
files_external: 1.22.0
files_pdfviewer: 3.0.0
files_reminders: 1.3.0
files_sharing: 1.22.0
files_trashbin: 1.20.1
files_versions: 1.23.0
forms: 4.3.1
impersonate: 1.17.0
logreader: 3.0.0
lookup_server_connector: 1.18.0
nextcloud_announcements: 2.0.0
notifications: 3.0.0
oauth2: 1.18.1
onlyoffice: 9.4.0
password_policy: 2.0.0
photos: 3.0.2
polls: 7.2.4
privacy: 2.0.0
provisioning_api: 1.20.0
recommendations: 3.0.0
related_resources: 1.5.0
serverinfo: 2.0.0
settings: 1.13.0
sharebymail: 1.20.0
support: 2.0.0
systemtags: 1.20.0
text: 4.1.0
theming: 2.5.0
twofactor_backupcodes: 1.19.0
twofactor_totp: 12.0.0-dev
twofactor_webauthn: 2.0.0
updatenotification: 1.20.0
user_status: 1.10.0
viewer: 3.0.0
weather_status: 1.10.0
webhook_listeners: 1.1.0-dev
workflowengine: 2.12.0
Disabled:
admin_audit: 1.20.0 (installed 1.13.0)
announcementcenter: 7.0.1 (installed 7.0.1)
bruteforcesettings: 3.0.0 (installed 2.4.0)
encryption: 2.18.0
files_rightclick: 0.15.1 (installed 1.6.0)
firstrunwizard: 3.0.0 (installed 2.6.0)
survey_client: 2.0.0 (installed 1.5.0)
suspicious_login: 8.0.0
twofactor_nextcloud_notification: 4.0.0
twofactor_u2f: 6.3.1 (installed 6.3.0)
user_ldap: 1.21.0

Nextcloud Signing status

No errors have been found.

Nextcloud Logs

No response

Additional info

No response

nextcloud / calendar