Should I Store User Data Locally on Device or Server Side Database

I'm currently working on a 'mental wellness' app, functionality for which include things such as;

• Making journal entries (typed and voice recorded)

• To Do Notes

• Setting Goals/Targets

• Recording affirmations/gratitude

My question is - Should I store the user inputted data as per above such as journal entries locally on the device, giving users the option to sync to their icloud or Google Drive? Or - save on a database on a server, as well as having the ability to use offline i.e. store locally and sync with server once online again.

My thinking was that with storing locally and giving the option to sync to the users iCloud or Google Drive, all the control is in their hands, therefore I/we never even see their data on the backend obviously as it never touches the server.

Would appreciate your opinion on the matter