[Bug]: Document templates broken

⚠️ 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

Create a new office document or text document in Nextcloud. The document creation dialog only ask for the filename but doesn't let me chose one of the Templates from the "Templates" folder

Happens to me on c.nc.com. On a fresh setup LTD it seems to work but this is also a older version (30.0.10) while c.cn.com runs on 31.0.4

Steps to reproduce

1. Make sure to have a "Templates" folder with some templates
2. Create a new document
3. You get only asked for a filename:

Expected behavior

I can chose a Template for the new document

Nextcloud Server version

31

Operating system

None

PHP engine version

None

Web server

None

Database engine version

None

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

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

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

Configuration report

List of activated Apps

Nextcloud Signing status

Nextcloud Logs

Additional info

No response

Start by reproducing the problem from the document creation dialog with a Templates folder containing templates, using the reported Nextcloud 31 setup. Inspect the dialog and template-selection entry point; done means creating a new office or text document offers the available templates. No files or tests are named in the issue, so identifying the relevant code and adding coverage will require repository research.