Does activating a magic item that does not specifically require an action still require an action?

Question

So for example Eversmoking Bottle states:

Smoke leaks from the lead-stoppered mouth of this brass bottle, which weighs 1 pound. When you use an action to remove the stopper, a cloud of thick smoke pours out in a 60-foot radius from the bottle. The cloud's area is heavily obscured. Each minute the bottle remains open and within the cloud, the radius increases by 10 feet until it reaches its maximum radius of 120 feet.

The cloud persists as long as the bottle is open. Closing the bottle requires you to speak its Command word as an action. Once the bottle is closed, the cloud disperses after 10 minutes. A moderate wind (11 to 20 miles per hour) can also disperse the smoke after 1 minute, and a Strong Wind (21 or more miles per hour) can do so after 1 round.

Using this item requires an action as stated in the description. However, items like eagle whistle and breathing bubble have no reference to what portion of the action economy they use:

Eagle Whistle

While you blow an Eagle Whistle continuously, you can fly twice as fast as your walking speed. You can blow the whistle continuously for a number of rounds equal to 5 + five times your Constitution modifier (minimum of 1 round) or until you talk, hold your breath, or start suffocating. A use of the whistle also ends if you land. If you are aloft when you stop blowing the whistle, you fall. The whistle has three uses. It regains expended uses daily at dawn.

Breathing Bubble

This translucent, bubble-like sphere has a slightly tacky outer surface, and you gain the item's benefits only while wearing it over your head like a helmet.

The bubble contains 1 hour of breathable air. The bubble regains all its expended air daily at dawn.

Answer 1

The magic item description will tell you if an action is required.

The rules for activating an item state:

Activating some magic items requires a user to do something in particular, such as holding the item and uttering a command word, reading the item if it is a scroll, or drinking it if it is a potion. The description of each item category or individual item details how an item is activated. Certain items use one or more of the following rules related to their activation.

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.

I’ve emphasized the important sentence above, and this second paragraph tells us that the rules are assuming that you will know if an item requires an action to activate. The only way you can know if an item requires an action to activate is that the description will tell you it requires an action to activate.