Have you confirmed that your MinIO configuration works in general with other mechanisms such as the MinIO client or the ? And that you’re using the proper URLs and configuration against MinIO?
My suggestion is make sure everything is compliant with the MinIO and s3cmd command line clients first - I’ve never heard of this “Cyberduck” client (for good reason: it’s Windows and Mac, I’m a Linux guy), and I can’t confirm it’s compliant with MinIO and other things since it says “AWS S3” on its thing and likely is designed for the full S3 API at Amazon, not S3-compliant/compatible items. Set up the minio client (mcli) on the command line at or near the box you’re trying to work with and then try and push a file manually to your buckets.
Additionally, keep in mind that DISCOURSE_S3_BACKUP_BUCKET with MinIO is designed to be its own bucket, not a subpath within an existing bucket (to my knowledge). It’s possible that may break things in the current setup as well, it’s why the example I wrote and the link to my “How to” that you provided has it as a separate bucket.
What I don’t have here is info on the specific request that actually was made - the URL path, etc. that was used by the system when it made that inquiry wiht the BadRequest. It looks like that’s becuase it only is INFO level logging. There’s no way to get a debug level of logging during the rake process is there @pfaffman (or others who are more familiar with the Discourse side of things)?
ALSO, make sure you also pass in DISCOURSE_S3_INSTALL_CORS_RULE: false for your Discourse configuration - if the app rebuilder/baker tries to push CORS rules it will result in an error message.