Juggluco saves unencrypted blood glucose relevant data on the device itself, but this is usually not available to other programs. Google Play and Android possibly collect information, but I haven't done anything to make this happen. The rest is totally under control of the user. Information can be saved with 'export' to a local file, but not directly on a Cloud server. With the 'mirror' function information can be sent to another IP address encrypted or unencrypted, but this will only be done under control of the user and to an IP address specified by the user. The user can make Juggluco send glucose values to a Nightscout server or to let other apps contact Juggluco via the web server or to receive glucose broadcasts.
If a user checks 'Send to LibreView' in settings and gives a working Libreview E-Mail address and password, glucose data will be sent to Libreview. Also account information given to Libreview will be received by Juggluco: FirstName, LastName, Country, DateOfBirth, GuardianLastName, GuardianFirstName. Use of this information by Juggluco is restricted to what is absolutely necessary to contact with Libreview and will only be used for contact with Libreview. What Libreview does with this information is unknown.
To take over an already started FreeStyle Libre 3 sensor, users have to give the same Libreview E-Mail address they used in the Libre3 app that activated the sensor and this is used by Juggluco to get an Libreview Accound ID from Libreview. The only use of this Account ID is sending it to the sensor, because when a different number is sent to the sensor it refuses to function.
If the user wants it, he/she can configure Juggluco to send glucose values to Health Connect (Left menu→Settings→Exchange data→Health Connect). This way other apps can make use of the glucose values, but no functionally of Juggluco depends on that. After Juggluco has written these glucose values to Health connect, which apps get access to these glucose values is controlled by Android and Health Connect.