Test first (Ctrl+A applies all transformations first):
1. The front of the model is facing Y-, and the "Apply Transformation" is not checked when exporting FBX → the X rotation in Unity is -89.98, not facing the camera, and the scale is all 100
2. The front of the model faces Y-, check "Apply Transformation" when exporting FBX → all rotations in Unity are 0, not facing the camera, and the scale is all 1
3. The front of the model is facing Y+, and the "Apply transformation" is not checked when exporting FBX → the X rotation in Unity is -89.98, facing the camera, and the scale is all 100
4. The front of the model faces Y+, check "Apply Transform" when exporting FBX → all rotations in Unity are 0, facing the camera, and the scale is all 1 (normal)
In summary, it is concluded that:
First face the model to Y+, select the model and press Ctrl+A to apply all transformations, and then you must check "Apply Transformation" when exporting FBX
(Before I didn’t dare to check it because I saw the skeleton collapse problem that Blender reminded me, but I haven’t seen this problem yet after I checked it)
Attached is a screenshot of the export:
