Reproduction steps:
1. Open the attached "Repro project"
2. Download the “user’s attached package”
3. Open Package Manager
4. Click on the + button
5. Press "Add package from tarball..." and select the “user’s attached package” file
6. After a while observe the crash

Reproducible with: 2021.3.35f1, 2022.3.19f1, 2023.2.9f1, 2023.3.0b6

Reproducible on: macOS Sonoma 14.2.1 (Intel), Windows 10 (by the reporter)
Not reproducible on: no other environment tested

Notes:
1. Opening the project again will successfully import the package
2. Might need to change the “user’s attached package” file extension from ".tar.gz" to ".tgz" so that it's possible to add the package with "Add package from tarball..."

First few lines of the stack trace:
0x00007ff7bff5e2bc (Unity) MonoBehaviour::Transfer<YAMLRead>
0x00007ff7bff7b8c5 (Unity) MonoBehaviour::VirtualRedirectTransfer
0x00007ff7c004cb37 (Unity) SerializedFile::ReadObject
0x00007ff7c0031b12 (Unity) PersistentManager::ReadAndActivateObjectThreaded
0x00007ff7c002f335 (Unity) PersistentManager::LoadObjectsThreaded