Hi, I don't think this site promotes specific security products, unless you mean this article: Troubleshoot Firefox issues caused by malware (but it doesn't suggest using AVG).

Searching on Mozilla community support for anti-virus compatible with Firefox produced responses touting AVG. But some time after I bought the expensive version of AVG, I received notice from Mozilla that it was stopping support for Firefox, my favorite and most used browser. That is why I was researching. I doubt I will continue with AVG, as I search for antivirus apps that can work with Firefox. What does the community recommend BESIDES AVG?

As far as I know, Mozilla does not have an official recommendation. You could ask on Reddit (r/Firefox).

Why does this site promote AVG for use on Firefox after I received notice that Firefox was no longer supported? Or is it now supported in full?

Hey! Firefox is still fully supported, that message might’ve been from an outdated plugin or a misconfigured site. AVG works fine with Firefox now. Try updating both Firefox and AVG to the latest versions and you should be good!