It seems that GenerateAuthoringComponentAttribute does not exist in Entities 1.3

[bitter rune]

Is there an alternative?

[wheat vapor]

Any code, tutorial existed before 2023 is now ancient and cannot be relied on.

The only alternative: write the authoring on your own.

https://docs.unity3d.com/Packages/com.unity.entities@1.3/manual/baking-baker-overview.html