Ubuntu Desktop 18.04.2 LTS, Firefox 68.0.1
I belong to forums that allow external HTTP links, such as images, within their HTTPS page. Mixed-mode pages are usually no problem with FF on other platforms, the help text says there is an "allow" process either with a warning dialog from the HTTPS lock icon; this "allow" (or whatever) button doesn't seem to exist. Alternately, there is a setting in about:config allowing mixed-mode passive content, but it accomplishes nothing under Ubuntu.
In short, I cannot get mixed-mode pages to display the HTTP content under Ubuntu/FF.
Possibly related... right-click on an HTTP image in many forum packages will have a "View Image" in the menu. This doesn't work, either, because FF changes the HTTP link in the HTML code to HTTPS. Also, these relevant about:config lines in OSX FF 68.0.1 - security.warn_viewing_mixed and security.warn_viewing_mixed.show_once - do not exist in Ubuntu FF 68.0.1.
At my wit's end, knowing just enough about this to get into trouble much less solve my issue.
TIA for any assist.
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