The version 12.0 UserInterface Java is only available in version 11.2 compatibility mode and will be the final version.
From version 12.0 onwards, all new features and enhancements will only be accessible via the Automic Web Interface (AWI).
Does the final Java UI (version 12.0) work with AE version 12.1?
The Java UI can login.
Some Objects are restricted, due to changes in AE V12.1.
Compatibility is not guaranteed.
Support will not accept issues reported for version 12.1 AE and Java UI.
Version 12.0 is supported until 2020-09-30, so there is no immediate pressure to upgrade.