You actually can’t turn it off, and they still refuse to publish the complete list of what is collected. You need an enterprise version to disable as much as they will let you, and even then, they still force quite a bit of collection.
They give you the option to fully inspect all the telemetry data your computer is sending, categorized by use.
https://docs.microsoft.com/en-gb/windows/configuration/diagn...
Seems like refusing to disclose what is collected would run afoul of GDPR. The law requires that "categories of personal data" be disclosed, and also that Microsoft's European customers have a right to a copy of their personal data. Are you claiming that Microsoft is not or does not intend to comply with GDPR? Or perhaps there is some other qualification implied; such as this only applies to non-European customers? If so what is your basis?