The software is on all phones but your local government has to make use of it. For the longest time the UK government didn’t use it and now they’ve adopted it and are obsessed with it.

They’ve now fortunately realized that irritating everyone with it means that they just turn it off eventually, so they’ve calmed down with it somewhat.

But I believe they are on by default so if you’ve never had an alert it’s probably because your local government don’t use it.