You have a few months before this will hit, but having a simple welcome screen where you inform about the crash dumps and how they help (show this fff) and let the user chose (remember - no bias toward the opt-in option) to give their consent is the correct choice.
Is the "no bias towards either ...

Regarding the privacy issue I would like to chime in (as a developer involved in GDPR) to let you know that making this opt-out is very likely to be a violation of GDPR. You must collect my unambiguous consent regarding that specific collection, storage and use of my data - crash reports/dumps when ...