HTMX has a very nice drag and drop extension I just found, though. And old-school forms can include image files. The little image preview can be a tiny "island of JS" if you have to have it.
I would consider that the bare acceptable minimum along an upload progress indicator.
But it can get a lot more complicated. What if you need to upload multiple images? What if you need to sort the images, add tags, etc? See for example the image uploading experience of sites like Unsplash or Flickr.
HTMX just ism't the right tool to solve this unless you're ready to accept a very rudimentary UX.
Please implement a multi image upload widget and then come back to argue about this.
I could be misremembering, but didn't browsers used to have this built in? Like there used to be a status bar that showed things like network activity (before we moved to a world where there is always network activity from all of the spying), upload progress, etc.
I don't remember if it was in Firefox, but SeaMonkey even has a "pull the plug" button to quickly go offline/online in the status bar.
Bizarre that "progress" is removing basic functionality and then paying legions of developers to re-add it in inconsistent ways everywhere.