In new SDK you can do it as per documentation:
By default, Crashlytics automatically collects crash reports for all
your app's users. To give users more control over the data they send,
you can enable opt-in reporting for your users by disabling automatic
collection and initializing Crashlytics only for selected users:
Turn off automatic collection by adding a new key to your Info.plist
file:
Key: FirebaseCrashlyticsCollectionEnabled
Value: false
Enable collection for select users by calling the Crashlytics data collection
override at runtime. The override value persists across launches of
your app so Crashlytics can automatically collect reports for future
launches of that app instance. To opt out of automatic crash
reporting, pass false as the override value.
Crashlytics.crashlytics().setCrashlyticsCollectionEnabled(true)