So I tried setting an upload rule from the "Managed Drive Options" . The rule sets uploaded files with suffix . html to be type text/html. However it doesn't change anything. I guess writing to a file on S3 from within Excel isn't seen as an upload.

Hi. I asked about this issue over in Stackoverflow, and the comment from an independent certified amazon developer was that the problem is likely to to do with Cloudberry as Amazon won't change the type.

https://stackoverflow.com/questions/55979474/why-do-excel-published-static-html-files-have-content-type-octet-on-amazon-s3

Uh. I don't suppose you have an upload rule? I guess I would use the CLI and the rule would be of the form

If suffix = .html then content type = html ??

I'm going to get a license anyway