Update: Still works for iOS 14.3 + watchOS 7.2
I can provide clean account to activate your Apple Watch’s ECG feature, please contact @hiraku_dev on Twitter.
Few months ago, I posted a tutorial about how to enable ECG feature of Apple Watch (oversea model). The restriction is: you must have an Apple Watch which is bought from ECG feature enabled region. However, Apple made a mistake on iOS 13.4 beta 2 and watchOS 6.2 beta 2, ANY Apple Watch S4 or S5 can enable ECG feature now!