Predictability beats perfection. A 20-minute wind-down that always includes the same basket of quiet toys will outperform a new rule announced in anger.
Keep a “evening shelf” at child height: a puzzle, a soft book, a plush. If they have to ask you to fetch play, they will ask for the tablet instead.
Older kids can handle a timer they can see. When it ends, the gadget lab or strategy duel is already on the table.