A guide on how to use the soon to be released Covid-19 tracking framework is available here
The framework implementation should be available as part of the v0.13 dev release coming out in the next couple of days in this week.
Stable channel - devices purchased from eShop - will receive the build by end of this week or early next week.
I can confirm it works well. I was a bit confused at first because “Exposure Notifications” didn’t show up in microG settings after installing the app but after a minute or so it did so I was just too fast there.