There are two ways:
- You may install the MicroG Exposure Notification version from /e/ OS “Apps”:
- Open Apps
- Go to Catogory (to the right of the ‘home’ icon on the bottom of the screen)
- Go to System apps
- Now you can find microG Exposure …
- You install “Corona Contact Tracing Germany” app from F-Droid (if the German app might suit for you)
For the reasons why it doesn’t work out of the box on /e/OS can be found when you search for “Covid” on /e/ forum (in short: some feared tracking so it was disabled by default).