I am trying to add a CalDAV calendar resource provided by a MacOS/Apple server in korganizer/akonadi. I am doing that by adding a DAV groupware resource. When I try to add a "Server Configuration" in the dialog and I click the Fetch button CPU/memory usage goes up but nothing ever happens.
The high resource usage is caused by a process called http* (Don't have the full name available now). The dialog lets me try to fetch calendars from other URLs once I kill that process.
That behavior is clearly a bug, but I wonder if there is a known workaround. Can I e.g. add a certain sub-directory of the DAV resource? I know from other cases that this can sometimes solve similar problem where akonadi is not able to fetch the calendar.

Can you start KOrganizer from the terminal and see if there's any odd output when you try to use the MacOS CalDAV calendar?

To complete my original request:
The process that gets crazy is called http.so.
I should also add that I am working with KOrganizer Version 5.4.3 from current kde neon user.
I don't see the problem with other resources and know someone who added the problematic one on an independent ubuntu with korganizer and dependencies installed.

Running korganizer on the command line does unfortunately not get me any output when trying to add the resource.
Same with strace korganizer.

Open up "kdebugsettings" and see if you can enable debug for "dav resources" (search for "dav"). Restart the whole PIM subsystem ("akonadictl restart" in a terminal) and try updating the calendar: see if any output occurs in the terminal.