Can I use Ultra watch without cellular?

You don’t need a cellular plan, and Watch will provide all functions—except cellular access—when operating without a plan. Watch will be able to initiate and answer calls via the iPhone, when within Bluetooth range of the paired iPhone, too.

The watch comes with cellular by default, but you absolutely do not need to set up the cellular if you don’t want to. It will ask you if you want to set it up and you can just click ‘Set Up Later’ or something that is related to that. (can’t remember the actual wording lol)

Yes, any cellular model of Apple Watch can be used without setting up Cellular connections.

The watch will behave like the corresponding GPS-only version when in range to the paired iPhone. In other words, it will work exactly as normal because that is the default mode for Apple Watch. All you won't have is the standalone cellular that is only used if your iPhone is out of range.

Jjandbabyp wrote:

Can i find an alternate cellular plan id mobile doesn't support it on the apple watch ultra

Apple Watch Family Plan (you may not like it)

Set up Apple Watch for a family member - Apple Support

Set up a family member’s Apple Watch - Apple Support

Some limitations: Cannot receive SMS/MMS messages, as that depends on a fully paired iPhone. Messaging is pretty much limited to Apple’s Messages, unless the messaging service provides an Apple Watch app. Alarms, alerts, notifications on the iPhone are not sent to the Apple Watch. Apple Pay via a credit card is not available. Also not available: Medications, respiratory rate, irregular heart rhythm notifications, ECG, AFib History, Cycle Tracking, Sleep, Wrist Temperature, Blood Oxygen, Walking Steadiness, Audiobooks, Camera Remote, News, Shortcuts, and the double tap gesture.

You must still use carriers that support Apple Watch Family Plan, but the iPhone and Apple Watch do not need to use the same carrier. And of course each device will have a separate phone number.

Can i find an alternate cellular plan id mobile doesn't support it on the apple watch ultra

Jjandbabyp wrote:

Can i find an alternate cellular plan id mobile doesn't support it on the apple watch ultra

This seems to be a different question, where you have an iPhone and a Watch and want the two to work together with a carrier that does not support Watch. AFAIK, the answer to that is either completely separate usage akin to a Family Sharing (isolated) Watch, or an unsupported mess. Or switching to a carrier with Watch support.