hola opensnitch package, for debian buster , works perfectly in debian buster , parrot os , kali linux . / I have not tried it on debian stretch or on ubuntu
Need installation of :
apt-get install libnetfilter-queue1 libnetfilter-conntrack3 python3-slugify python-pyqt5 libc6 python3.7
Package : opensnitch_1.0.deb
sorry for my bad english