WebDav Server not working

Hi there,

I would like to use the WebDav Server Application found here: http://extensions.xwiki.org/xwiki/bin/view/Extension/WebDAV%20Server#Information

When I copy the mentioned .jar files into the WEB-INF/lib directory of the xwiki-webapp, like I should when following the instructions, xwiki doesn’t work anymore after I restart tomcat. The wevb.xml of course is configured.
Tomcat says that there is nothing found in /xwiki.
I figured out that this happens after copying the “org.xwiki.platform:xwiki-platform-oldcore 9.11” jar into the directory.
I’m very happy getting some hints on what I’m (probably) doing wrong.

Xwiki was installed on Debian 11 using XWiki Tomcat 9/PostgreSQL package

No other software/extension is installed by now. System is “vanilla”.

Thanks for your help.