There are some situations where I'd say opt-in telemetry, properly messaged and with transparency/user-visible logs about what is uploaded, is fine.

But your tool is specifically for handling highly sensitive credentials, and telemetry can be used as part of an attack surface. For your tool, any hint of telemetry, even opt-in, would be a massive red flag.

Having a feedback button that launches a plain old mailto: link might be a good balance to provide an additional mechanism to learn about users' pain points.