My group libraries are not imported from Zotero: only my personal items are. The folder “Group libraries” is created but empty.
As indicated on your help page, I did set the permissions to “Read Only” in “Default Group permissions”.
Is the import of group libraries broken for anyone else?
Wonderful, it worked. It cost me 20$ to buy enough Zotero storage to inherit the ownership, though – hence the potential usefulness of importing libraries without being the owner, or at least to precise it somewhere in the doc.