Having trouble importing 3D character model into Unity (normals and mesh errors)

Question

I'm facing a ton of issues with trying to import a 3D character model into Unity. When I try to load the model into Unity, I'm greeted with Normals and Mesh errors

When I export the model from Blender to FBX format, and then import it into Unity, I consistently encounter the following errors:

1. "A polygon of Mesh 'ModelName' is self-intersecting and has been discarded."
2. "Can't calculate tangents, because mesh 'ModelName' doesn't contain normals."

*These errors occur on multiple meshes within the model.

So far, I've tried the following to fix these errors:

• I've tried various export settings in Blender, including different smoothing and apply modifiers options.
• I've checked that the model is correctly rigged and has armatures.
• I've attempted to recalculate normals in Blender's Edit Mode (may try again, since it has been quite iffy sometimes to do so, and I'm not yet acquainted with Blender).

*I'm running Blender 3.6.4, and Unity 2022.3.9f1 as program versions.