I think this is a bug but I don't know enough about svg images to be sure. On export, links to svg images produce an <object> element rather than an <img>. Here's the docstring of the function (from ox-heml):
Return \"object\" embedding svg file SOURCE with given ATTRIBUTES.
INFO is a plist used as a communication channel.
The special attribute \"fallback\" can be used to specify a
fallback image file to use if the object embedding is not
supported. CSS class \"org-svg\" is assigned as the class of the
object unless a different class is specified with an attribute.
Neither chrome nor firefox can display these objects. On the other hand, if I modify ~org-html--format-image to~ treat svg images just like other images (in an <img> tag) then the image displays just fine. Is there a reason we use the object tag instead/ If not, what's the best solution? I na try to work on a proper fix.