In brief, after installing the Pale Moon browser [Ubuntu 16.04] I discover that even after COMPLETELY removing Firefox via Synaptic, the latter nonetheless still serves as default browser.

As example, when clicking to open an html link to ebay within the Sylpheed email client, which action constitutes an auto-call to the default browser, a browser page loads with the word 'Firefox' on top and the words 'Pale Moon' underneath.

Looks to me like this stems from the integration of Firefox-as-default into the Ubuntu kernel, making Firefox in Ubuntu much like the old controversy of (and subject of a class action law suit) against Microsoft for its handling of the Internet Explorer browser, back when IE was ingrained as 'default' in the Windows APIs and could neither be separated from Windows Explorer nor deleted.

My expertise in software issues pretty much ends at the GUI and I thus know of no solution to this perplexing circumstance in which I must wear Firefox like the proverbial albatross around my neck.

I do okay using Terminal and would enjoy severing Firefox from my system entirely, which at this point in time seems impossible. But I'm open to suggestion.

'Word on the street' has it that Mozilla is implementing a sympathetic response to Google's new policy of censure, which thing flies in the face of the 1st Amendment and is therefore despotic.

. . . Any of you experts out there in Software-Forum-Land have suggestions re ways and means of fully removing Firefox so that Pale Moon receives auto-calls and runs in FULL-DEFAULT mode?

Thanks and a good day to all who read this post.

M.

Sounds like some of the configuration files for FF are still hanging around.

Try:
OR>
HTH

Palemoon is Firefox, just an older and rebranded version.

Also this:
... i don't know how to say this politely - it's just wrong.
the kernel has nothing to do with what gui applications run on your desktop.

Thanks to Ztcoracat for the kind advice and I will take it.
Thanks also to ondoho for using polity, or at least trying to.
. . . But ondoho, you could have expressed your displeasure with my conjecture about the kernel in any number of different and TRULY polite ways.
As example, you could have written, "BTW, the kernel isn't involved in any way with gui-based apps." Neat, sweet and petite.
Additionally, Pale Moon is described as having a different code system entirely when compared to Firefox.
MoonChild Productions (I think they're called), asserts that Pale Moon is distinctly different.
I agree. Pale Moon is definitely NOT Firefox.
As to any conjecture that it is. . . that's just wrong.
Have a better day, ondoho.

You're Welcome mike3644.

Did that issue with Firefox go away?

I've never tried the Pale Moon browser. How's it's performance?

wrongly quoted.
according to their own website:
palemoons user agent string:
do with it whatever you like.
the answer to your original question lies here.

i'm out.

update-alternatives is probably what you're looking for.

$ ls -l /usr/bin/x-www-browser
$ ls -l /etc/alternatives/x-www-browser