"Sorry...that page seems to be missing" is shown on the browser when clicking the help icon on a Panel Renderer component

How to reproduce:

1. Create or open a Unity project
2. In the top menu, click (GameObject > UI Toolkit > Panel Renderer)
3. Press the “?” button in the Inspector window within the “Panel Renderer” component
4. Observe the browser window

Actual result: “Sorry... that page seems to be missing!” shows up
Expected result: Documentation page is displayed without errors

Reproducible with: 6000.5.0a4, 6000.5.0b5, 6000.6.0a3
Could not test with: 6000.0.73f1, 6000.3.14f1, 6000.4.4f1 (Panel renderer was introduced in Unity Editor version 6000.5.0a4)

Reproducible on: macOS 26.4.1 (M1 Max)
Not reproducible on: No other environments tested

Note: The opened link is https://docs.unity3d.com/6000.5/Documentation/Manual/class-PanelRenderer.html (when using 6000.5.0a4)