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.
Moodnotes - Capture your mood and improve your thinking habits
Habitica - Habitica is a free habit building and productivity application.
JournalBook - A truly private, offline-first, personal journal
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Notion Bullet Journal Template - Template with goodness of both Notion + bullet journal
HabitBull - HabitBull