But to answer your question, anyone can host Sia nodes. Here are their docs on that: https://support.sia.tech/category/0OpBuOHIVD-hosting
Is there a simple way right now to use another storage backend than Sia? E.g. If I have a group of people that want to participate in hosting, but only want to host data from the people in the group?
Essentially, can you use dgit to store a repo decentralised without having to set up git synchronisation tools, but while still having control over the hosting infrastructure?
We've had a lot of experience with running IPFS nodes internally, that might be a great option for you in this case? We are in early stages and will add more adapters as feedback informs.
Also, its open source and we would love PRs :) - the storage interface is pretty straight forward:
https://github.com/go-git/go-git/blob/master/storage/storer....
Here is an example within dgit: https://github.com/quorumcontrol/dgit/blob/master/storage/ch...