Chromium browsers lack side tabs and horizontal tabs make zero sense. I believe that Firefox (and its derivatives) is the only option which is open source.

(yes there are a few vertical tab extensions for Chrome, but they are all incredibly lame as they do it by injecting an iframe into each webpage (!!))

I actually like Vivaldi's "tab grouping" feature better than tree side vertical tabs. I use Firefox tho, because I don't want to give chrom* based browsers any more market share

I like Ungoogled Chromium: https://ungoogled-software.github.io/ungoogled-chromium-bina...

At least for testing, I use Firefox as my daily driver.

Firefox still exists and is still great. So far rumors of its death are greatly exaggerated.