I don't limit myself at all. When I want to do any activity that seems to be dopamine-fuelling (emails, HN, Reddit, Stripe, other metrics, even company Intercom), I just have to set a timer to certain duration. I can reset, snooze, or extend durations however I want. No rules. Just the action of setting a timer.
Oddly it has made myself way more conscious and intentional. Resulting in almost no actual distractions when I do want to focus. Technical tricks (blocking apps, websites, or DNS) are unfortunately too gimmicky because it's so easy to bypass. And personally I had no results with those.