Magic items in the DMG that require an action to activate excluding casting a spell:
A-D
Alchemy Jug, Amulet of the Planes, Apparatus of Kwalish, Armor of Invulnerability, Bag of Holding, Bag of Tricks, Bead of Force, Bowl of Commanding Water Elementals, Brazier of Commanding Fire Elementals, Candle of Invocation, Cap of Water Breathing, Carpet of Flying, Censer of Controlling Air Elementals, Chime of Opening, Cloak of Invisibility, Cloak of the Manta Ray, Cube of Force, Daern's Instant Fortress, Dagger of Venom, Decanter of Endless Water, Deck of Illusions, Dimensional Shackles, Dragon Scale Mail, Driftglobe, Dust of Disappearance, Dust of Dryness, Dust of Sneezing and Choking
I imagine a few of the ones I left out b/c they said 'cast this spell' will be reworded to allow their use.
If you feel the Fast Hands ability to activate a magic item is not useful if it can't be used with scrolls I don't know what else to say.