I mean, I like Firefox, but I’d love to see Vivaldi based on Firefox/Gecko. There’s Floorp, which is similar in some ways but it’s more like an Edge built on Firefox than Vivaldi.
Edit: Thank y’all for your answers. :D
I want to link !@bdonvr@thelemmy.club 's post because it is a similar quesion. https://thelemmy.club/post/718914
Blink is a fork of WebKit wich is a fork of KHTML, KHTML exist since the '98, the codebase isn’t that younger too. Was tweaked by Apple then by Google, with some features that don’t exist on other engines.