If you go to the dialog where you link to the popup you will
notice that the Link To button is disabled as soon as you select a
popup, auto sizing or custom size. That is because for whatever
reason, popups are not intended to be used in that way.
I know that you can select in the way you did and then change
from Display in Frame to popup and the target will still show but
the Link To dropdown is disabled and therefore the content is
ignored.
If you create a topic with just the image in it, then you can
link to that as a popup. Like it or not, that appears to be the way
it was designed.
Images are included in the output but only if the link is
created in a way intended by the designers.
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