about:debugging - yes. But that seems to see the code in a different context (pid? [probably]) than the page that I actually want to debug - youtube. Moreover when I set a breakpoint in the code I’ve gotten from about:debugging then trigger the relevant operation in a youtube page, the code doesn’t break.
That’s 82.0.2. Downloaded the Aug 1 nightly which is 81.0a1 and added the addon I want. Here, the addon does appear in the FF debugger in the same youtube page (pid) and I can set a breakpoint and it successfully breaks there.
My guess as to what’s changed (between 81.0a1 and 82.0.2) has something to do with this warning seen for the addon in about:debugging (in 82.0.2):
So the addon, in the case of 82.0.2, acts not as event page but as a persistent background page - except part of what I"m contending with is I don’t know, yet, how to debug it as a persistent background page.
I can debug just fine in 81.0a1 - but that’s neither what I want or need. Want to understand how the addon works with the latest release versions of FF.