I believe opera had tabs for a while before Firefox. It was one of the main reasons I think I used opera for a good long while.
What a fun time.
https://github.com/marklieberman/foxygestures
https://otter-browser.org/ (Tools → Preferences… → Advanced → Mouse → [X] Enable mouse gestures)
And although browsers are no longer distinctly better than each other, I still donate to Mozilla.
Opera added true tabs some versions later, while still hanging someway on the MDI-tradition.