As GDPR makes it clear, users should be able to request to view and delete their generated data from any application. If it’s a Local first application, it would be trivial if it’s already on their own machine.
Things like their own content consumption history (eg YouTube, SevenMind, etc) is usually not saved on their own machine.
I find it morally wrong to put their own data behind a paywall as part of a sustainable business model, for example there are some services where you need to pay a premium to export your own metrics or data.