Agree completely for Android. I've used Focus since it came out and set as primary browser because it is so light. It works great from Materialistic (HN Reader) and Reddit App or for one time website browsing. It also allows opening in Firefox or chrome if site is too broken though that is usually ad or captcha related.

I setup DNS66 easily and that helped with some ad heavy apps as well. Only issue is it cannot be used with actual VPNs.

I open Firefox manually if I want a heavier browser with tabs and ublock or umatrix but focus is usually first.