Eli Zaretskii <eliz@gnu.org> writes:

>> Date: Tue, 18 May 2021 11:45:08 +0100
>> From:  Joe Corneli via "Emacs development discussions." <emacs-devel@gnu.org>
>> 
>> Hello, the attached SVG file was made with M-x org-latex-preview.  It
>> includes an embedded PNG file.
>> 
>> The source is this LaTeX-in-Org oneliner, together with the PNG.
>> 
>> $$\mathit{Hello} \includegraphics[width=2cm,natwidth=445,natheight=661]{/home/joe/tools_for_thought/Tft1st.png}$$
>> 
>> The generated SVG image displays correctly in Mozilla Firefox 88.0.1.
>
> FWIW, I don't see the embedded PNG in Firefox, either.  Not even in
> the latest version 88 of Firefox.

Have you installed the PNG file in the location expected by the SVG
file?  Alternatively, you can adjust the embedded file name in the SVG
file.

For example, I saved the two files as /tmp/foo.svg and /tmp/foo.png and
edited the xlink:href attribute in /tmp/foo.svg to point to
/tmp/foo.png (a relative file name also works).

The result renders fine in Emacs 25 and 26 (w/ ImageMagick), Emacs 27
and 28 (w/ Cairo and w/o ImageMagick), as well as Firefox 86.0.1, with
the system librsvg 2.50.3: