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.
Taskade - Make lists, organize your thoughts, and be inspired to get things done. Taskade is a collaborative space for your tasks.
HabitBull - HabitBull
Done? - A TODO list for productivity and procrastination lovers
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
ToDoBot - Slack-native todos right in your Home Tab