ACL Folder/Directory Access dialog does not display existing directory access control entries, starting in HCL Domino R10 on the Linux platform.
(RedHat Linux, CentOS Linux. We also tried Ubuntu - which is NOT supported - and the issue is also on that Linux distribution, as well.)
As of 2020/06/10, HCL has issued SPR# MOBNBPQQEA.
We can add new folder/directory access entries using the Domino Admin client dialog.
To edit existing ones, you must SSH to the server, and use vi to edit the folder.
$ ssh firstname.lastname@example.org
$<lotusnotes> cd /local/notesadmin/
$<lotusnotes> vi FolderNm.acl