The Orion browser uses WebKit. Currently macOS and iOS only, but they're working on a Linux version.

Apple's laptops for a while now have had an option (in trackpad preferences) where you can place two fingers on the trackpad and click the button to get a right-click. It's easy to get used to, and obviously only requires one hand, so you no longer *have* to have an external mouse and you no longer *have* to use option/ctrl.

I use my MBP all day every day and I estimate that 99% of my clicks are left-clicks, so I have no problem with having one physical mouse button; In fact I much prefer having a huge single button to hit with my thumb.