I recently received several .numbers files with data that I want to relate to points on a map using FME. I had to ask the sender to export them from her Mac as Excel or CSV. Fortunately, she was willing and able. This is the first time that I have received .numbers files, so I don't know if this is a larger problem for the community. For the current project, I anticipate receiving more data in this format.
This from the web:
"You can only open NUMBERS files with Apple Numbers in macOS and iOS.
You can also upload NUMBERS files to the iCloud version of Numbers in your web browser (requires an Apple ID). This is helpful for Windows users who don't have access to the Mac or iOS versions of Numbers. In the iCloud application you can view, edit, save, and download NUMBERS files."