I may or may not have other browsers installed on all of my other boxes, but I know for certain that Firefox is installed on every single one --
Since WebKit is all but dead, there are only really two left to test in. Blink and Gecko. These are about all that's left of any real consequence these days, so I sometimes question why I might have these different brands installed that are all drawn from the same thread.
Usually if I want to test in Blink, I'll use Opera, and as for Gecko? Well, since it's exclusivity has been around since before the dinosaurs roamed the planet, I'll use it always first and foremost for testing, and all other things internet.
I've used Gecko since 4-ever and if Presto was still around, I'd probably be using that one too.
I think that the crew over at Firefox is giving it the old college try with this most recent update -- Not as "clunky" I've noticed -- Of course I've yet to try it over on the Windows box, and since nearly everything on the planet clunks over there (that isn't Microsoft exclusive), I'll take my time getting to it.
Disclaimer: I use pseudonymised (hashed) visitor fingerprinting for contextual delivery and analytics.
For a better idea of what/how Mozilla is targeting with their FireFox resist fingerprinting mode: * Security/Fingerprinting [wiki.mozilla.org]
This is a good first step in that it tackles some 'low-hanging fruit' used by many fingerprinting scripts. For a couple of the more widely used it looks as if it drops probability from ~90% to ~65%. Not as much effect on more advanced algorithms: 99.99% to 97.2%. I read that Mozilla is using Tor browser obfuscation/resistance to fingerprinting as their guide; how far they can go that route before it begins to impact user==site convenience and so complaints and usage will be interesting to watch.
Plus Firefox (and Safari and Vivaldi) are minor players at this moment. Perhaps, they can ride PII to increased uptake... As with climate change PII is a broad but quite thin concern of most people (especially in the US) where direct friction/cost causes support to drop drastically. If years on years of data breach after data breach has little impact...