Categories don't display, but are present in HTML page code.

[swappart]

I'm not sure what the issue is, but if I change the following to display: block, the categories can be seen.
.o-list { display: none; margin-bottom: 0px; padding-left: 0px;

(Magento version 2.4.4)

[swappart]

I see what the issue is. The browser is refusing to load the font-awesome stylesheet because it violates the content security policy. As a result, the plus and minus fonts aren't displayed and there's nothing to click to display the categories.