I have found this Q/A explaining some items a Thief can use through their Fast Hands feature as well as this tweet (though now unofficial) from Jeremy Crawford saying that Fast Hands does work with a shield.
The Fast Hands feature's description states:
You can use the bonus action granted by your Cunning Action to... take the Use an Object action.
And then the "Use an Object" section states:
When an object requires your action for its use, you take the Use an Object action...
The DMG (page 141) states this about activating magic items in particular:
If an item requires an action to activate, that action isn't a function of the Use an Object action, so a feature such as the rogue's Fast Hands can't be used to activate the item.
Shields require an action to don or doff and "Shield, +1, +2, or +3" are listed under the "Magic Items" section of the DMG on page 200.
However, it is still unclear to me whether donning/doffing a shield counts as either "Using andan Object" or "Activating a magic item", so I am wondering:
How does Fast Hands interact with mundane and magical shields?
