Assume your data will be used not only for training a newer model (which, why not?), but maybe for something else (later on).
If you or a company requires privacy, you can run your own AI locally: notebookchat.com/index.php?topic=315954.0 ("Your own ChatGPT, offline: AI without the cloud on your laptop") and comments.
Communities around local AI e.g. reddit.com/r/LocalLLaMa.
ChatGPT, Gemini, Claude and Copilot all work without a subscription. Each one still takes something in return, whether that is ads, your chats as training data or a smaller model. Here is what each free plan offers, what is switched on by default and which settings to check before your next chat.