From the FAQ[1]:

  > Will you know what topics exist, can you spy on me?
  > If you don't trust me or your messages are sensitive, run your own server.

This is the way. No pinky promises in whitepaper format[2] that leave out the most important bits, no meticulously constructed but entirely meaningless marketing statements[3][4], but unassuming and deferential logic with a mitigation path.

1: https://ntfy.sh/docs/faq/#will-you-know-what-topics-exist-ca...

2: (warning: redirects with identifiers, how ironic) https://www.whatsapp.com/security/WhatsApp-Security-Whitepap...

3: https://privacy.microsoft.com/en-us/privacy-report

4: https://www.apple.com/privacy/