Steps to reproduce:
# Open the attached project
# Select sprite under "Assets/Bed/Magic House bed sprite.png"
# Click Sprite Editor in the inspector
# Select Secondary Textures in the top-left dropwdown
# Select NM_Test from the list
# Observe the sprite preview area

Expected result: the normal map is displayed like a normal map

Actual result: the normal map is displayed as a red transparent texture

Reproducible with: 2023.2.0a5, 2023.1.0b6, 2020.3.43f1

Note: this is reproducible on MacOS. On Windows the normal map is displayed correctly.