I installed linssid from appcenter and it wont launch. It only launchs from the terminal using sudo. how can I fix this?
I think this is because an outaged version of linssid in appcenter (2.9 I guess). The way how to get Super User privileges in GUI has meanwhile probably changed (you will need administrative privileges to sniff network traffic).
You can download an updated version from here and install the deb manually or add a ppa to your system and install via terminal:
sudo apt-add-repository ppa:wseverin/ppa sudo apt update sudo apt install linssid
Please consider this (old but still relevant) question and answer when adding external repos to your system.