There is an active effort called that patches the old code to work with new S3 storage backends. If you are a developer, you can self-host the uploader widget on your local machine and point it to the Archive's S3-compatible endpoint.
Here is the blueprint for a perfect upload using the HTML5 tool: internet archive html5 uploader 164 best
The default uploader flattens your folder structure. Version 164 respects relative paths. If you drag a folder named "Manuscripts/Chapter_1/", the archive will retain that directory structure. This is crucial for software repositories or complex web archives. There is an active effort called that patches
Uploading – Troubleshooting - Internet Archive Help Center internet archive html5 uploader 164 best