Regions for Apple Watch Ultra cellular connection

UAT??

The ability to use cellular signal depends on the following information from Apple...

To cover the LTE and UMTS bands used around the world, there are two separate cellular models for Apple Watch Series 8, Apple Watch SE and Apple Watch Ultra. They have been optimised for use in the country of purchase, and not all models work in all countries or regions. There is no single model that supports cellular service worldwide. To see which network providers in your country or region offer cellular service for Apple Watch, refer to the chart below. 

Apple Watch - Carriers - Apple

Main thing is No Apple Support and No Warranty for Watches bought outside your home country

There is only ONE carrier in Cyprus who supports Apple Watch and that carrier is Cyta. You MUST be using them as your carrier for your iPhone. If you are not using Cyta for your iPhone, you won't be able to establish cellular service on your watch.

See this link from Apple about carriers throughout the world who support Apple Watch --> Apple Watch - Carriers - Apple

As you see from the table there are two main types of Ultra, one for USA, Canada, Mexico and a few similar territories, and one for the rest of the world. So IF you want to change your iPhone carrier to one of the carriers who provide an eSIM service to the Watch you may be lucky. You still have no Apple Support in Cyprus so good luck with any hardware or warranty problems.

As lobsterghost1 and others have said, the cellular compatibility is basically USA devices on North American networks, and Rest of World devices anywhere except North American networks. However, it can be more complicated with Apple Watch because it uses eSIM which must be configured by your network. Some networks have been reported as refusing eSIM devices not marketed for their region.

the best advice I can offer is that you should ask the question direct to the network you intend to use the imported device. If you are lucky they will say it will be supported. If you are unlucky they will say NO! The big grey area in the middle is they will say it is not rejected but they make no promises until you try it.