If anyone else is not able to upload submission images and instead receives IO error messages using Firefox, the work around is to instead use Chrome. The same work around may be used if attempting to insert images into a forum page you may wish to comment on.

If you are using the insert image tool as shown on the menu bar, your image will not appear, rather only a clickable file name shown in red will appear. To work around this issue, use the upload file tool to upload your image, then click inline insertion to have the image appear rather than just the file name.

As for attaching INP files, I've tried dragging them in or using the upload attachment tool during the submission process and in both instances the file does not appear on the final submission. The work around here is to post the submission, then once the thread is open, post an additional reply and drag your file in to that second reply.