This “proprietary telemetry” is basically malware, just, it was put on the thing at the factory. Once a system is fully rooted by malware, the least-bad option is to nuke it entirely and install from scratch.

In this context where the locked-down device probably also doesn’t have a fully open source kernel and drivers, this becomes a bit tricky. Better just to use a device that doesn’t have malware on it in the first place.