I think GPS is essential. Tie it to a location - if stolen, it won't operate.
Then a way to text you if it is moved outside the designated area. Telling you where it is.
At that point, I suppose it would still be worth stealing just for the battery? A hard problem to solve.
The problem with gps is it doesn't work (reliably) under trees which many lawns have. Since trees are common in yards they need something else anyway and at that point you can get rid of the gps
Not super helpful if it doesn't have a way to communicate to the outside world. Some of the companies solve this by adding a cell module that can send an SOS, but it usually requires a monthly/yearly fee to maintain the cell connection.
In my case, my lawn isn't easily accessible and also not visible from the street (because the house and garage is between the street and the garden), and I trust my neighbors. So, I think (I hope) this isn't so much an issue for my case.
I think the eufy has also an optional GPS module just for this purpose, to better track it. I don't think this GPS module has any other purpose (e.g. it would not be used for navigation). But I didn't really checked the details on this.
I have seen this a few times for such robots, that you can buy an optional GPS module for tracking.
I think GPS is essential. Tie it to a location - if stolen, it won't operate. Then a way to text you if it is moved outside the designated area. Telling you where it is.
At that point, I suppose it would still be worth stealing just for the battery? A hard problem to solve.