The doc string for org-export-with-latex describes how to select mathjax, verbatim output, or not to export LaTeX at all, although it goes further to say:
If you prefer, you can also request that LaTeX fragments are processed into small images that will be inserted into the browser page.
But no value is actually listed for requesting that. I've tried setting org-export-with-latex to 'dvipng and "dvipng", with no success either way.
The only way I've obtained the desired result is with #+OPTIONS: tex:dvipng. Unfortunately, that method would require modifying each and every org-mode file.
What's proper way to specify the dvipng export mechanism globally?
Note: Actually, no value for org-export-with-latex seems to have any effect. Without #+OPTIONS: tex:dvipng, I always get mathjax, unless I set org-html-mathjax-template to "", in which case I get verbatim-style output -- again, regardless of the value of org-export-with-latex.
Emacs 26.1, org 9.1.14
