I did it: after years of happily using Brave, and over a decade hiatus in general, I'm now using #Firefox. (For now.) After three or four hours of messing about with user.js prefs to get things just how I want, installing and configuring extensions, logging in to all of my websites and finally setting Firefox as my default browser, things seem to finally be falling into place. I'll report back after a few weeks; the only test will be real life usage.
My first assistive technology foible with #Firefox is that text selection with #JAWS is fiddly at best, a nightmare at worst. Rarely does JAWS highlight the correct text--and sometimes, it doesn't highlight anything at all. Other times, it will highlight the beginning few characters of a paragraph and then just drop the rest. #NVDA, of course, doesn't exhibit this behavior. I'll continue troubleshooting but a bug report to Vispero is probably in order.