Blink is a fork of the WebCore component of WebKit, and aside from sandboxing, has remained relatively similar to WebCore. As such, Brave necessarily is based on WebKit via transitve relation. V8 is a JavaScipt engine, not a browser rendering engine.
Practically, there are only two rendering engines left, 1) WebKit (itself derived from KHTML) and its derivatives such as Blink, and 2) Gecko and its derivatives such as Goanna, (though I guess somewhere someone must be using Flow, which apparently is not based on either, but it is proprietary, thus it will have no derivatives or be used by any other browser other than Flow).
Thanks for pointing that out. I was mis-reading some of the comments here saying the DDG browser in question is Webkit (because it's a MacOS browser only, for now). So is it based off Chromium as the base then?
Practically, there are only two rendering engines left, 1) WebKit (itself derived from KHTML) and its derivatives such as Blink, and 2) Gecko and its derivatives such as Goanna, (though I guess somewhere someone must be using Flow, which apparently is not based on either, but it is proprietary, thus it will have no derivatives or be used by any other browser other than Flow).