Is it a full blown browser with support for all capabilities (basically a web-view with no title bar?) or does also it attempt to block all fatigue-related bloat, ads, moving parts, auto-play videos,...?
It will clear all cookies / logins very often, so you'd basically start from scratch, logging in and so on. It is cumbersome, and for me it was totally enough friction to not fall into old habits.
(So yes, there are potential loopholes, but they are uncomfortable to crawl through. Dopamine is all about friction, I guess)
Yes! There was some paperwork to do with Apple (it is a manual approval process), and it got the entitlement to be the iPhone's system browser. For Android, things were a bit easier.
So after installing Leash and selecting it as the system browser, Safari can be deleted.