The fourth Android 10 beta updates for the Galaxy S9 abd S9+ were released last week. That update fixed bugs and brought the new Android January 1, 2020 security patch.
Samsung has begun rolling out new updates for the Android 10 and One UI 2.0 beta for both the Galaxy S9 and S9+. This updates comes with bugfixes. The build for the Galaxy S9 has the serial number G960FXXU7ZSLC. The firmware of the Galaxy S9+ has the serial number G965FXXU7ZSLC. The firmware of the beta updates on both devices is around 140MB in size.
To get the beta update, users of the Galaxy S9 duo have to be enrolled on the beta program, then they can download the new updates under the settings menu. Samsung is looking at releasing the stable updates later this month or early next year.