Odinote is developed in the open — every channel below reaches a real person (usually within a couple of days).
Open an issue on GitHub Issues. Please describe what you did, what you expected, and what happened instead — screenshots help enormously.
The GitHub Discussions board is the project's town square: feature requests, usage questions and feedback all live there, and other users can vote on your idea.
For security reports or anything you'd rather not post publicly, open a private security advisory on GitHub, or start a discussion and ask to take it private.
Odinote is free and has no premium tier. If it's useful to you, you can buy me a coffee on Ko-fi — every donation goes into development time.