Updates in v0.11:

• Small change to the camera far clipping plane to improve the shadows in Unity 2020.3
• Bug fix to the JigsawPuzzleGenerator script so that it no longer throws an error when building for release
• Specific versions of the package have been generated for Unity 2019.4 (LTS) and 2020.3 (LTS)
  •  (a version for Unity 2021.3 (LTS) will be made available as and when Unity releases that version) 

Note: for Unity 2020.3 the way preview packages are handled is slightly different to before, so the Vector Graphics package (which the jigsaw puzzle generator relies on) is no longer visible through the Package Manager.  Instead you will need to open the Package Manager and then click on the + dropdown icon in the top left of the window (see attached screenshot) and then select the "Add package from git URL..." option.  Add com.unity.vectorgraphics and the package should install automatically.