Hi Mia, here's how I solved this same issue: https://blogs.perficient.com/2020/10/12/episerver-and-alternate-text-for-images-in-the-tinymce-rich-text-editor/
Basically, at render time of XhtmlStrings we can tap in and adjust the img tags accordingly. Hope this helps.
Fingers crossed that Epi fixes this in a future version!
In cms version 11.18.1, when we drag and drop an image into TinyMCE, the alt text is set to the image filename. I know this is a bug that hopefully will be fixed soon, and i think the fix you are working on is to make the alttext empty instead.
We have a custom property on our ImageFile for alt text and since we don't want the editors to have to write a new alt text every time they drag and drop an image into the xhtml it would be great if the alt text was included when dropping the image. Since this is a custom property I understand if its not possible, but it should be possible to create a configuration where we can configure the TinyMCE to set alt text to what we want? (i.e. onImageDrop => alttext=imagefile.alttext)