Today an update was pushed out to the Windows client, targeting Linux users who are running the game using Steam's Proton compatibility layer. There was an issue with Electron - the wrapper used to turn a browser based game into an application - which caused drop down menus to be rendered under the application window. This behavior has been fixed, and now the game should be fully functional under Proton.
Ideally, I would like Linux users to be able to run the game using the Linux native application, but some distributions with various mixtures of Desktop Environment/Window Managers have issues with the Electron based application. I am continuing to work on improving native Linux support wherever possible, but today's update at least provides a fix to the Proton compatibility fallback that all Linux users have available.