Thanks for trying that, @mst. I wasn’t able to reproduce that with the Sage theme, I get folders and files on npm install (example below).
I found one other report of this in the past. It turned out to be specific to the user’s environment:
You could also try npm install --loglevel verbose to see if logs explain why files aren’t being created, or explore environment variables to check for differences in environments (e.g. run env on macOS/Linux, compare the output when it works and when it does not).
You originally suspected that it might be “related to how Local mounts the site folders into its environment, possibly an issue with the filesystem sync layer on macOS Apple Silicon.” But Local doesn’t mount any filesystems, it runs natively using your real filesystem, so the cause is likely elsewhere.
