From the page:

https://doc.qt.io/qtdesignstudio/qtdesignstudio-mcu-treadmill-example.html

If user clicks the link to Figma file:

It leads to this link:
https://git.qt.io/public-demos/qtdesign-studio/-/blob/treadmill-revision-revision/examples/TreadmillMcuDemo/figmadesign/McuDemo.fig

Which results in:

The link cannot be accessed without login to gitlab. The right link should be:

 
https://git.qt.io/public-demos/qtdesign-studio/-/blob/master/examples/TreadmillMcuDemo/figmadesign/McuDemo.fig?ref_type=heads