Figured I’d provide a bit of general insight into cross border charitable donations due to this question Questions about the OSRA announcement - #8 by JM_ROS
(Specifically the cross border part - nuances about OSRA membership will be in the main Q&A thread)
There are organizations which can ‘bridge’ donations between countries for a small fee. I have used https://www.kbfcanada.ca/en/ before, they’re part of https://myriad.org/ The group you choose may have minimum donation levels as well. However, the OSRF or a program within it must count as a valid charitable purpose under the tax regime you are within. I don’t know German laws, but as an example none of the current programs of the OSRF count under Canadian law, so even using a group like the above can’t create a Canadian tax deduction.
Hope that helps!