This is related to packages upgrade:
- If you create 3D URP template project, go to Package Manager and see that some packages has newer versions - upgrade one package and when done that package folder will be shown as empty
- If you create 3D URP template project in one Unity Editor version and then open this project in newer Editor version - all upgraded packages will have empty folders.
- *I am adding link to a thread with repro steps and video in a comment*

How to reproduce:
# Create a new project using the 3D (URP) core Template
# Open the Packages folder in the Project window
# Observe the Project window

Expected result: The installed packages are visible in the Packages folder in the Project window
Actual result: The installed packages are not visible in the Packages folder in the Project window

Reproducible in: 2023.3.0a14, 2023.3.0b1
Not reproducible in: 2021.3.33f1, 2022.3.16f1, 2023.2.4f1, 2023.3.0a13

Reproduced on: Windows 11 Pro
Not reproduced on: No other environment tested

Notes:
* The user states that it is only a visual bug, and the packages are correctly installed
* The bug is specific to the 3D URP core Template

Workaround: Right Mouse Click in the Project window, then click on “Reimport All“