Public posts, photos, captions, and comments across both apps.
Meta uses public posts and photos going back to the start of the account.
Public posts, photos, captions, and comments across Facebook and Instagram, going back to the beginning of the account. Private messages are excluded unless you send them to an AI.
There is no switch. There is an objection form, and Meta decides. In the EU and UK, GDPR Article 21 gives a right to object and the form is generally honoured. Elsewhere the form exists but the outcome is discretionary, and Meta has stated that public content is used regardless.
Do not mark this "done" on the user's behalf when the form is submitted. Mark it "submitted" and let them set it to done when a confirmation arrives.
A submitted objection, not a switch. Outside the EU and UK it may be refused.
Every service on that list buries its opt-out somewhere different. Don't Train On Me puts all of them in one checklist in a panel beside your browser, walks you through them one at a time, and helps you confirm your privacy settings on the ones that expose a setting it can read. Free, no account, and nothing you tick leaves your machine.