Regarding the black box issue. I believe this is due to a recent change in Godot. I encountered a similar issue, and switching from Forward+ to Compatibility rendering mode resolved it. However, be aware that Compatibility mode comes with some drawbacks.
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There might be a different fix too.
- Change rendering method to
Compatibilityor - Disable VSync in
Project Settings > Display > Window > V-Sync Mode: "Disabled", if you need a fps cap consider usingProject Settings > Application > Run > Max FPSinstead
I learned this from developing a game that needs a transparent background. It was from a person named KitzuGG.