Might want to look into Fred Trump.

I’m not very IT savy so I’m not sure if I have anything to contribute. In general there’s various trackers on the market. Some use GPS, some use Bluetooth and some use radio. All of them have respective proprietary apps. Maybe looking into these apps could give some insight?

The Nut tracker (GPS) is only 15 € and I can at least open the app on my degoogled phone.

This is a bit of a long shot. Does this work with tracking devices? I’m looking for a degoogled way to track my cat and somebody linked me here.