Plugins from PP3 UC don't show up as Available Plugins

It is not possible to install plugins from the new NetBeans Plugin Portal 3.0 in the Apache NetBeans IDE 11.0. Despite the update center for version 11.0 [1] containing two plugins none of them is displayed in Available Plugins tab of Plugins dialog

[1] http://netbeans-vm.apache.org/pluginportal/data/11.0/catalog.xml.gz

Steps to reproduce:

1. Launch Apache NetBeans IDE 11.0 with empty userdir.
2. Invoke Tools > Plugins from main menu and switch to Settings tab.
3. Click Add button, type New PP3 UC as Name and paste [1] link into URL. Click OK button.
4. Uncheck all other update centers but leave New PP3 UC as active.
5. Switch to Available Plugins tab and click Check for Newest button.

Expected: NB Figletize and Upload Files Button plugins are offered for installation.

Actual: Available Plugins table remains empty.