There is a Raspbian armhf package in the debian section as well… I just enabled the Raspbian 10 build (unforunately I need to manually add new distributions, so give me a heads up if that happens…), so that should be available soon as well.
The build source for that is obviously available at Show home:uroni / urbackup-server - openSUSE Build Service , you can even create an account fork that and submit changes (or I can add you as maintaner to the project).