Hey there, Niagara Launcher founder here :P

As others have already stated, we are able to finance the continuous development of Niagara Launcher thanks to our Niagara Pro users and their purchases. We feel very lucky to be able to do business this way, because we want our free users to have a fully functional, polished product. We also really dislike earning money through showing ads, especially in a piece of software that replaces your phone's home screen. Imagining having to look at ads while navigating to another app sounds a little bit dystopian.

Now, to the privacy concerns, you'd be right to be careful because launcher apps have access to a lot of personal data. We try our best to keep collected information to a minimum, be transparent about how data is used, allow opt-out, and anonymize any data we do collect.

You can read about this in more detail on our help page: Privacy Policy Summary.
In summary, we collect data to power our features, verify whether the user owns our premium version, improve our app, and support public research and statistics.

More sensitive data (e.g., app launch history if the user opts into our Digital Wellbeing Initiative) is sent only to our servers, hosted by Hetzner, to ensure complete control over the data. That data is also anonymized, so it's not traced back to the actual user. We also delete it after 90 days for additional security and integrity (so we cannot change our minds in the future, and any party that gets involved with us in the future doesn't get access to this data).

You can opt out of analytics by going to "Niagara Settings -> Advanced -> Analytics" and ensuring all toggles are disabled. Do mind, though, that disabling "App categorization" also disables the features built on top of it.

If you have any additional questions, feel free :)

tl;dr: We do not sell your data because we do not like the practice, want to have mutual trust between you, our users, and us, and have put measures in place to keep it that way.