There are different ways in which you can support SEOnaut. If you find it useful, you can upgrade your account from the free plan to the monthly subscription. That way, not only you are supporting the project but also getting some benefits, like being able to add up to 5 projects and having a crawl limit of 5000 URLs per project.
You can also sponsor SEOnaut via Github sponsorship, where you can opt-in for different tiers, from a one-time donation to a monthly sponsorship that will get your logo in this very page.
Other than that, your help improving SEOnaut will be more than apprciated. Report any bugs you come across, make feature requests, help writing documentation, and If you are confortable with code, feel free to make pull requests to the Github repository.