How do I sync my iCloud work calendar with Thunderbird?

I've been following this guide on how to sync my iCloud calendars with Thunderbird's own Lightning service. It has worked so far, until I tried to sync my work calendar. With the method described in the article, it appears to have no calendar ID, it only says "work?clientBuildNumber=blablablah" in the link retrieved by the Firefox inspector.

Thus, I've tried to type the resulting CalDAV address like:

https://pXX-caldav.icloud.com/XXXXXXX/calendars/work/

However it doesn't seem to work, as the calendar doesn't connect at all and becomes greyed out, unlike with the other calendars I already added. Those became active from the get go and synced correctly.

A person in the comments asked the same thing and apparently they found a solution in this thread, but I do not have a Mac, just PC, so I have no idea on how to apply that solution to my situation.

How can I solve this?

Thanks!