Seems the server is 50 USD/month for 50 clients. Since it is FOSS, I suppose you can self-host?
This seems shady:
"* In addition to standard version available on the Google Play, Traccar Client for Android comes in a special hidden version. It includes modifications to make the app less visible to the phone’s owner. Name is changed from “Traccar Client” to “Device Settings”. Default Android settings icon is used as an app icon. After first start, the app removes itself from the launcher. To open it again dial 8722227 (TRACCAR)."
I highly doubt that's GDPR complaint. Then again, it is a Russian company who sell their server capacity in USDs.
This seems shady:
"* In addition to standard version available on the Google Play, Traccar Client for Android comes in a special hidden version. It includes modifications to make the app less visible to the phone’s owner. Name is changed from “Traccar Client” to “Device Settings”. Default Android settings icon is used as an app icon. After first start, the app removes itself from the launcher. To open it again dial 8722227 (TRACCAR)."
I highly doubt that's GDPR complaint. Then again, it is a Russian company who sell their server capacity in USDs.