PSA: Gemini apparently trains on chat history even on paid personal accounts

There's a big Tell HN thread today saying paying for Gemini on a personal account doesn't opt you out of training on your chats, only Workspace/business accounts get that by default. Same week there are reports of OpenAI quietly re-enabling training on Codex chats. If you use these for experiments with private data, what's your setup now: business tiers, local models, or just accepting it?