I get multiples of the same error as OP, mainly about Landmass but some others too.
The fix/workaround that works for me is:
Project Settings → Packaging → Advanced → Uncheck “Exclude editor content when cooking”
Not sure yet of the consequences but at least packaging works and my build plays as expected.
Edit since people keep seeing this post (March 2025):
The main consequence is that it may lenghten build times and increase the build size.
The proper thing to do is go through each error and follow the trail to where editor-only content is being referenced, and if it can’t be avoided one workaround is making copies inside the project content and switching the references to that.