Written by the person who wrote the app, which means answers are slower than a call centre and considerably more useful.
The FAQ covers what it runs on, what it connects to, where passwords are stored and what the app sends anywhere.
Email kyle@hankinsoft.com. If you are writing from inside the app, use Help → Email Support: it fills in the version, build, macOS version and channel for you, and nothing else.
Never send passwords, private keys or tokens. Nothing about diagnosing a problem requires them, and no legitimate support request will ever ask you for one.
Email the same address with "security" in the subject and it will be treated as the priority. Please give details privately first rather than posting them publicly.