It's better to use bluetooth fake location app to unlock ALL functions.
For the details, see the comments below, like https://gist.github.com/imReker/fba069c6cae7407509863b0ed78da2a7?permalink_comment_id=5889305#gistcomment-5889305
After a lot of testing by the people in the comments, it looks like only ECG will work.
So just replace the first three files:
com.apple.HeartRate.notifications.plist
com.apple.HeartRate.plist
com.apple.private.health.feature-availability.plist
Any apps that support Bluetooth LBS fake location, eg, AnyGo or iAnyGo (you need to pay for a month, or use some magic), move the location to USA, open Health Checklist on phone and turn on everything.
You can check https://www.tenorshare.tw/change-location/hypertension-notifications.html, start reading from 2.2 section.
Or this https://uuzi.net/apple-watch-hypertension/