https://wccftech.com/watchos-7-4-will-enable-ecg-in-australia-and-vietnam-next-week/

Apple will releases watchOS 7.4 next week to Apple Watch users around the world. It will enable ECG in Australia and Vietnam.

Next week, Apple will release iOS 14.5 and iPadOS 14.5 to everyone around the globe. But, at the same time, Apple will be seeding other software as well, including watchOS 7.4.