Nice work on the SFZs.
I was able to upload SFZ versions of several pianos to the pianobook library in the early days (such as here: https://www.pianobook.co.uk/library/1911-bechstein-upright-andrew-ward/). So I think rather than splintering the repository in various places, we might want to figure out why the previous way of uploading seems not to be working. Could it be that the system is working but you haven’t given it enough time?
When I uploaded in the past, I would put the original name of the piano followed by (SFZ version). I never received any feedback, but the versions eventually showed up on the site. I don’t think there are many people working on the site, so you might just want to give it some time.
If you want to put your SFZ mappings on github as well, that is fine, but please don’t give up on the pianobook library.