Who knows what skeletons are still hiding?
Go and have a look? https://github.com/brave/brave-browser
My argument is that Brave is a Chromium browser with questionable business goals, but it is also the most private and secure, open-source, mainstream* Chromium browser. These keywords cannot be said about Vivaldi, Ungoogled Chromium and many other projects unfortunately.
That said, I primarily use Vivaldi because of its customizability and added features, something Firefox seems to reduce with every new version.
- Not quite on Edge or Opera level, and no accurate data can be found due to the removal of unique user agent, but nonetheless I'd argue it is more popular than others of similar kind.