[jimbosis]

(In case you haven't heard of it and it proves helpful to you and/or someone else:)

Have you heard of Epyrus?

Homepage: http://www.epyrus.org/index.html

(The download link is easily found there, as well as git repository and forum links.)

It's based on UXP (the Unified XUL Platform) and is thus related to the Pale Moon browser (which doesn't bother me). I've been using it on Linux as a way to have an "older Thunderbird" look and feel, e.g., I have real scrollbars, and the "Send" button didn't mysteriously vanish from the Compose window with no way to get it back upon some "from the ground up redesign" upgrade.

EDIT: Typographical error, phrasing.