The nativeFabricUIManager is likely used during the first render in one of your installed libraries.

nativeFabricUIManager global const won't always be initialised before the end of the first render, as it is dispatched during the first render.

It's best to check for it during the second render.

Link to source where it is dispatched: https://github.com/facebook/react-native/blob/c3ea606660ab0540882b6ded3b85e88c24c88b3a/packages/react-native/ReactCommon/react/renderer/scheduler/Scheduler.cpp#L117

While not particularly documented, this fact is known among React Native library maintainers: https://github.com/software-mansion/react-native-gesture-handler/blob/b3d8fd91dca195267bdc33aa20fd6f5cd37d7fe2/src/utils.ts#L46

I recommend searching for it inside the node_modules folder, and removing the library you find it in.