Hello flow!
I'm sorry for the late reply. I think you can fix the error by opening the PreviewRenderingViewport script, replacing line 18 with
[Export] private Godot.Environment _environment;
and then removing line 11, that says
using Environment = Godot.Environment;
Don't forget to save and press the "Build" button in the top right corner of Godot afterwards.
Please let me know, if this fixed your issue. I will then include this fix in the next version accordingly.