By default, this is what Delete Actions does. Calls a cloud function to delete the user document from the user's collection.
Secondly, when you set rules on another collection like tagged users.

//Delete the USER COLLECTION\nexports.onUserDeleted = functions{CLOUD_FUNCTIONS_REGION_SENTINEL}.auth.user().onDelete(async (user) => {\n\n  let firestore = admin.firestore();\n\n  let userRef = firestore.doc('users/' + user.uid);\n\n  await firestore.collection(\"users\").doc(user.uid).delete();\n\n});

But when you want to delete more than users collection. We set Tagged user property. Where it finds other collection where user might have information in. The same way I advised, using Loops where
\"tagged by\" (ref) == user to be deleted (ref)
But this deletes the entire document. So in your case. You can either edit the rules manually from Firebase Rules or run a loop before the delete user actions and delete those fields manually.

//Delete the USER COLLECTION + OTHERCOLLECTIONS WHERE USER IS TAGGED\nexports.onUserDeleted = functions{CLOUD_FUNCTIONS_REGION_SENTINEL}.auth.user().onDelete(async (user) => {\n  let firestore = admin.firestore();\n  let userRef = firestore.doc('users/' + user.uid);\n  await firestore.collection(\"CollectionName\").where(\"user_ref\", \"==\", userRef).get().then(async (querySnapshot) => {\n    for (var doc of querySnapshot.docs) {\n            console.log(`Deleting document ${doc.id} from collection products`);\n      await doc.ref.delete();\n\n    };\n  });\n  await firestore.collection(\"users\").doc(user.uid).delete();\n});

How do you set tagged users for collections in Flutterflow?
The check box on the right means what I mentioned above. \"Delete this collection\" when \"Delete User Action\" is called.

how to add user account deletion in app ?