Once Dovin’s loyalty ability resolves, the damage prevention continues to apply even if Dovin leaves the battlefield.

In a multiplayer game, if you leave the game after Dovin’s last ability resolves but before your next turn begins, its effect lasts until your next turn would have begun. It neither expires immediately nor lasts indefinitely.

Dovin’s loyalty ability can target any permanent an opponent controls, not just one that can deal or be dealt damage.