How do I export heart rate data that is not associated with an activity (i.e., HR data taken throughout the day)?
You can export it in the FIT file format (on the Daily Summary page), or you can access the JSON data with browser's DevTools (F12). On the Network tab, enter the search expression "dailyHeartRate" to find it.
It is not there anymore or is it due to language?
I switched to English and no change
Yes, Garmin removed it. Only the JSON data from DevTools remains. Or requesting a full data dump at https://www.garmin.com/en-US/account/datamanagement/exportdata/