It's never a good idea to upload anything personal or confidential to cloud-based AIs, as many of them use your prompts for data collection or training purposes. If you want privacy, it's best to run LLMs locally. If a site does not state that sign-up is required, you can still use it without logging in, but you will face stricter limits and have access to fewer models.

Bypassing chatbot safeguards (aka jailbreaking) is against the TOS of most AI, so use them at your own risk.

Keep in mind that most of these will require signup, and in most cases can only generate relatively short videos.