BrainModular

When I open Usine Pro I get a message at the top of the screen saying it can't connect to your server. That would be because my DAW is offline. How can I stop it trying to connect in the first place?

yes, it's because Usine use the Internet connection for addons and online help ( if you set it in your global setup/interface ) but addons can't be disabled
but don't worry to much , it's just a message in the console, no consequences

It would be good to have an option to disable it though - sometimes hosts or plugins phoning home can cause instability and it's undesirable behaviour anyway

Usine detects if your are or not connected to Internet.
If you're not, it displays the msg but does nothing....
It's globally safe, but you're right an option in the setup could be useful.