I have installed BOINC platform. And now it launches on OS startup. Can't find it in
Startup Applications Preferences. Please help me to prevent it from start using command line. Thanks in advance.
You can use
sudo systemctl disable boinc-client to stop it. If it still starts up on boot, use
sudo systemctl mask boinc-client, which should entirely prevent it from starting (you can't start it manually then either, which is...not ideal).