FWIW, Vivaldi attracts a lot of the FF power users that updates like Quantum abandoned. Vivaldi honestly wipes the floor with Firefox feature-wise especially for tab organisation, but the fact it’s Chromium might push some people away.

It would’ve been nice if they used Gecko, but eh. I went from FF to Vivaldi to now, the Firefox fork Pulse. It’s a bit janky sometimes, but with native vertical tabs and the Simple Tab Groups add-on I love it enough to use it as my main browser, and there’s little to no bloat. There’s also Floorp, another Firefox fork, this time from a Japanese community, which AFAIK predates Pulse and is inspired by Vivaldi, implementing some of its features like Tab Workspaces. Worth mentioning for those wanting a more Vivaldi-like experience.