My machine is using Debian. You are right: the directories in /home have proper permissions, so subfolders should not be accessible by other users. Thank you for the hint.
root@ns8test:~# ls -l /home
insgesamt 28
drwx------ 4 collabora1 collabora1 4096 21. Jan 12:09 collabora1
drwx------ 4 ldapproxy1 ldapproxy1 4096 21. Jan 10:31 ldapproxy1
drwx------ 4 loki1 loki1 4096 21. Jan 10:31 loki1
drwx------ 4 nextcloud1 nextcloud1 4096 21. Jan 10:38 nextcloud1
drwx------ 4 openldap1 openldap1 4096 21. Jan 10:33 openldap1
drwx------ 4 traefik1 traefik1 4096 21. Jan 10:25 traefik1
no problem, this was a good question, I recall something with first nethserver 8 installation and debian where the /home was world readable, we have fixed the issue but only for newer installations, former installations should fix by themselves the permission IIRC