If you have a web browser with "jar:" URI scheme, it can also display EPUB files, although not the table of contents list. You will have to write "jar:" before

If you have a web browser with "jar:" URI scheme, it can also display EPUB files, although not the table of contents list. You will have to write "jar:" before the URL and "!/" after the URL, to make a directory listing of the file. (It also displays Gempub files OK, with the additional code that I have added to support Gemini file format) Some other features such as "last paragraph", accessibility, annotations, etc, could be made to be supported even for any HTML file (in some cases, only for local files), even if it is not EPUB. (Since, EPUB is already HTML, anyways)