[grounder]

Try Firefox Nightly for the native sidebar vertical tabs. That and native tab containers make Firefox work really well for me.

[karteum]

If you want vertical tabs, built-in adblocker, and more generally are looking for a lightweight and free (as in free speech and as in free beer) browser, you may look at https://www.falkon.org/ (made with QTwebengine i.e. Blink)