How to reproduce:
1. Open the user’s attached “My project.zip” project
2. In the Hierarchy, select expand “Canvas” GameObject and select “UI_Main Camera”
3. In the Inspector window, change the value of Camera “Viewport Rect” W or H to “1.0000001”
4. Observe the result

Expected result: Cube is red
Actual result: Cube is dark

Reproducible with: 2021.3.29f1, 2022.3.7f1, 2023.1.8f1, 2023.2.0b4

Reproduced on: macOS 13.4.1 (Intel)

Notes:
-when the pasting value to Camera “Viewport Rect” fields, it doesn’t show the pasted new value
-when inserting “1.0000001” into the Camera “Viewport Rect” fields, it shows 1
-not reproducible if changing the value of Camera “Viewport Rect” W or H to “1.00000001”
-reproducible just with "Screen Space - Camera" and "World Space" Canvas Render Modes
-reproducible in the Editor and Standalone Player (macOS)
-reproducible with X and Y values in the 3rd step if the value is “0.000000000000000000000000000000000000000000001”