How is Vivaldi with security? I had used it for a few months a few years ago before I started caring for my own privacy but never looked in to it. I know it’s by former opera devs but that’s the extent. Is it FOSS?

Just switched to it the other day. I liked the letterboxing and its assistance to reduce fingerprinting and OOTB ublock origin. And the familiarity of Firefox made it an easier transition from reg Firefox.