Comment by Aaargh20318

> This can only ever be opt-in if you want to stay on the legal side of the GDPR

The GDPR only applies to personal data. You can collect things like performance data without opt-in (or even an opt-out option) as long as you are careful to not collect any data that can be used to identify an individual, so no unique device IDs or anything like that. Of course, you should be transparent about what you collect. You also have to be careful about combinations of data points that may be innocuous on their own but can be used to identify a person when combined with other data points.