After some work,  we've launched an offline Leaderboard for everyone who wants to compete with their friends at a LAN party :D
You can enable it in the in-game Settings.

We've also been notified about some issues regarding the online Leaderboard. We've tackled them and you can now upload your scores properly. But you need to log out first and also delete the "tutorial.save" and "factory.save" files. You can find them in %APPDATA%\Godot\app_userdata\Rostige Pipe\ on Windows and in ~ /.local/share/godot/app_userdata/'Rostige Pipe' on Linux.

Here are the full patch Notes for 1.1.0:

• Added offline Leaderboard functionality
• Fixed an issue which made you unable to upload highscores
• Fixed persistent Boss UI after completing the Factory level
• Added direction hints in the factory
• Changed Assembly Name