this works for me:
(Note the nethserver specific home directory for a (local LDAP/AD) user.)
$ pwd
/var/lib/nethserver/home/mark
$ ls .ssh/
authorized_keys
$ cat .ssh/authorized_keys
ssh-rsa <long key>== mark@domain.org
for root ssh login it is business as usual
# pwd
/root
# ls .ssh/
authorized_keys
# cat .ssh/authorized_keys
ssh-rsa <long key>== mark@domain.org
Hope this helps…