Afaict the niche they attempted to fill is the one Firefox already fills on desktop, a highly customizable browser with extension support. (Firefox does not support extensions on iOS, apparently has no plans to do so, and as I understand the support is somewhat limited on Android as well). I switched for about a year because they delivered what seemed like a serious effort at that with their initial release. After seeing basically zero effort at addressing very fundamental bugs in that support in that year, I switched back. As far as I’m concerned their battle is already lost.

The iOS codebase is the only one that potentially has any value to the OSS community; this kind of "enjoy our garbage!" source release really irks me.