Happy to see new browsers appearing. Up to this day I'm still trying to find a good replacement for Conkeror(http://conkeror.org/), with little luck. webmacs was quite promising for a bit but it just petered off.
Check Nyxt (https://nyxt.atlas.engineer/). Based on WebKit (actually designed to be engine agnostic but WebKit is the only one supported) instead of Gecko, and scripted (also developed) in Common Lisp rather JavaScript.
And if you need something a bit more robust and based on up-to-date FF code and maintained I've been toying with LibreWolf (https://librewolf.net)