So I installed ettercap like 5 times today in differents ways : with and without the sudo command, in graphical or text-only mode. Trying -reinstall, remove&install.
And the same error occured again : Error : 2, No such file or directory [/build/ettercap-wpDeUF/ettercap-0.8.2/src/ec_conf.c:load_conf:277] Cannot open etter.conf
So I found it with locate and it results 3 directories : - /etc/ettercap/etter.conf
- /usr/share/ettercap/doc/etter.conf.5.pdf
So I tried to edit the etter.conf file in the first way and the file is empty.
I checked all the threads in kali's forums and search during 4 hours.

Thank you for your help !