I am a K-12 public School District in Arizona and I am using Duplicati as part of my backup plan / strategy. With our very limited budgets, this is not only an affordable solution; it is also a solution that works much better than paid one’s. I am still setting the based backups. So far, I have a couple TB done and already used it for one user who needed a previous version of a document. I would love to provide a donation but as a K-12 school district, it is challenging. However, I will direct anyone who would like to make a contribution to make one to Duplicati. On behave to all the children we serve as a K-12 school, thank you to all the developers and other volunteers behind this project.
Thank you for taking the time to let us know how Duplicati has worked for you! 
Thanks for the kinds words. I am very happy to hear that it works for you!
I know that some companies need to get an invoice etc. We have set up an “OpenCollective” group that you can direct people to if they want to donate with documentation:
https://opencollective.com/duplicati