I guess it's really safe cause it's open source, you can make notes on your habits but don't really do that. Its simple. Really fast. Haven't found a way to connect it to notion. In general it's a great app to track you habits. Does its job. Not more, not less.
Habitica - Habitica is a free habit building and productivity application.
Zoom - Equip your team with tools designed to collaborate, connect, and engage with teammates and customers, no matter where you’re located, all in one platform.
HabitBull - HabitBull
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.