You can force Firefox to display dark mode in web content (even with privacy tweaks enabled to resist fingerprinting or tracking), by setting the two following hidden prefs in your user.js:

// PREF: enable a Dark theme for browser and webpage content
// [TEST] https://9to5mac.com/
user_pref("ui.systemUsesDarkTheme", 1); // HIDDEN
user_pref("browser.in-content.dark-mode", true); // HIDDEN

Yes of course. I hadn’t slept when I replied, how embarrassing to miss that. You can enable CNAME uncloaking in Brave, which I suspect draws them to a parallel. It would be interesting to see the test repeated with the setting enabled. Since one has to (or had to) enable it in uBO also, it would only be fair to compare apples to apples. As I said, the blocker in Brave is based on uBO anyway. To be clear, and as I’ve said before, I’ve daily driven Firefox since the beginning and run uBO in medium mode. I’m not shilling for Brave here, simply pointing out that the differences are small (much of the code is shared with uBO) and it does certainly render faster.

Brave isn’t represented anywhere on the graph? Unless I’ve misunderstood you. That’s a comparison of Firefox with various ad blockers, and uBO with and without CNAME unclocking enabled. Brave also uncloaks CNAMEs, so that’s one place they are equal. Chromium based browsers do lack some abilities compared to Firefox, however. I have daily driven Firefox since the first day, but Brave and Blink/Chromium based browsers are undeniably faster at rendering (unfortunately).

And thirdly, I have seen no mention of anything like ublock’s blocking modes (block 3rd party scripts/frames). Can you quickly select an element to block in brave?

You can enter as many custom filter rules as you like, with adblock syntax support. You can select an element to block, yes.

A baked-in content blocker like that of braves loses because it isn’t extensible.

In what way? I use(d) Firefox since the very first Firebird days, and Netscape Navigator before it, and I’m practically married to uBO (don’t tell my wife!). That said, Brave’s ‘shields’ blocker is just skinned uBO with some tweaks. It can add custom cosmetic filtering rules, additional adblock format filter lists, disable or enable JS (globally or per-site) and has built in fingerprint resistance. Aside from the differing UI, I genuinely can’t think of anything overtly missing as such.