You can support Ferdi's development by contributing to the project.
If you want to contribute to Ferdi, too, take a look at https://github.com/getferdi/ferdi for more information about the project or https://github.com/getferdi/ferdi/issues to find a list of bug reports and feature requests others have posted.
Even though Ferdi can be used for free, we still have to pay bills to keep Ferdi's infratructure up and running (Servers, licenses etc.).
So if you are satisfied with Ferdi and want to give something back, please consider donating or sponsoring Ferdi at https://opencollective.com/getferdi.