Rockin Robbins is a user and fan of Vivaldi. Drop him a PM.
Vivalid was put together by former Firefox staff that were not happy with the way things went down the drain at Mozilla, and left, more or less in anger.
Firefox since a few weeks now also runs under the Chromium engine. Thats why many secvurity and privacy addons for it are broken, or have been rewritten but work not well, and many modders have left Firefox, becasue they took the sh!t from angry users although it is not their guilt, but Mozilla's. Privacy protection , once the prime argument in favour of Firefox, has seen an extreme, wanted weakening. Firefox, Vivaldi, Chrome - i do not see big differences anymore.
I was thinking about getting Vivaldi myself, but since I learned it also uses Chromium, I fail to see the point in switching.