If you are arriving late in Dubrovnik the only ferry would be to one you mentioned.
To return, if you are foot passenger, use ferry nona ana from Sobra to Dubrovnik dep 17:40 arrival 18:55
gv-line.hr/raspored.php?linija=3
Not sure about Jadrolinija one, but they do run ferry ever day from Mljet to Dubrovnik.