Belcher is a fast, non-interactive combo deck built around Goblin Charbelcher and various artifact/land-based mana acceleration like Lotus Bloom and Whir of Invention, so our sideboard options are limited since most of our hate (Fatal Push, Damping Sphere) doesn't meaningfully slow them down. Collector Ouphe shuts off artifact activations, completely stopping Goblin Charbelcher itself as well as Lotus Bloom and anything fetched by Whir of Invention. Our best plan remains racing them with our own fast combo starts via Delighted Halfling and Devoted Druid, since this matchup comes down to who assembles their engine first rather than sideboard technology.