It doesn’t have nearly as much features as Nova sadly

If you want you can try Floorp if you’d like to use Firefox based browser. It is really customizable, although it is missing a lot of things that Vivaldi has, like split screen and tab grouping. But it has an enhanced support for tree style tabs which is a big plus in my opinion.

It also has double sidebars so I can put tabs in one of them instead of the top of the screen and hide the titlebar without having to modify userchrome.css. That’s one thing I missed from Vivaldi when I moved to Firefox.