Samsung has just issued a hotfix update to the second Android Pie beta on Galaxy S9, launched yesterday. It is only 90 MB in size and patches two significant issues that slipped in the major release. Users complained about losing mobile data connection and having trouble launching some apps.
To get the Pie beta that moves to One UI on your Galaxy S9 or Galaxy S9+, you must be part of the Samsung Members program (also known as Samsung+ in the United States). Through the dedicated app you can see the whole log, but your software should be updated through the Settings menu.