A new hotfix for Astride is now available. Here are the changes/fixes that have been made.
You may have to restart your Steam client if the hotfix is not immediately available.
Fixes & adjustments
Fixed a bug that left some players stuck on a black screen at startup. This fix is only for a specific issue related to missing save data and there might be other bugs resulting in getting stuck on the black screen. Please file a bug report if this happens.