So for the building of an elixir app with flyctl, I would just install the necessary things inside the nixpkgs and change the flox build steps to deploy to flyctl?
Regarding the things that keep running, I’ve been able to reproduce:
- run hivemind
- kill the terminal without killing hivemind first
Now all the process that hivemind started are still running 
Expected behaviour: killing the terminal should kill all applications that hivemind runs as well.