The backslashes are required to interpret the $ literally; you can see from the estimate when I granted read access to the system directories that it was successfully ignored.
The read access permissions work for me now, and I’m happily using Kopia; the underlying issue seems to be the same as this thread: for some filesystems Kopia hard fails on stat even when ignoreDirectoryErrors is true, and will stat directories before checking if it should ignore them.
- nickersonm