Basically impossible, or at best very impractical. Companies change their product after you buy them. This is not a hypothetical - this happens all the time. It happened to you, and to me.
My most recent example: I wanted to calibrate my display using a "calibrite display pro hl" and suddenly got prompted with a software update. After updating, an account is suddenly required. This device is way past its return date. I cannot return it. I'm now stuck with a device that cannot be used with their software without creating an account.
Another example: Philips Hue devices were changed to require an account.
These days I focus on getting commercial variants of devices, since they usually don't have cloud or smart crap in them. For example, there's commercial variants of many TVs. They don't have smart crap in them and are designed for 24/7 usage.
Completely agree that this kind of behaviour should be illegal. My thoughts are products should work from purchase with their offered feature-set (or be forced to recall), have a factory reset mode, and an opt-out of updates.
My most recent example: I wanted to calibrate my display using a "calibrite display pro hl" and suddenly got prompted with a software update. After updating, an account is suddenly required. This device is way past its return date. I cannot return it. I'm now stuck with a device that cannot be used with their software without creating an account.
Another example: Philips Hue devices were changed to require an account.
These days I focus on getting commercial variants of devices, since they usually don't have cloud or smart crap in them. For example, there's commercial variants of many TVs. They don't have smart crap in them and are designed for 24/7 usage.