I'm currently developing an integration with Nest Device Access and I've seen that the same device shared between different nest accounts don't have a matching device-id.
When requesting the devices list,of two different users, the device-id reference of the same phisical nest doesn't correspond.
I guess that the device-id is set per user. My problem is that I need to identify a physical nest between accounts, and for that I need a unique device-id to identify it, which I'm unable to find. Is there a way to find this unique Id?
There is no way to uniquely identify a device across multiple users. As you indicate, it is both per-device and per-user.