This is not an issue but a suggestion:
I don't have a dedicated server nor a good upload speed to use ServerSync. That's why I would like to host my mods and configs on the cloud.
I don't know how would you scan the files on the cloud to assume there's an update. Maybe you could just scan one text file indicating the version and compare it client-side.
Hope you consider my suggestions, thanks.

Most cloud services have public API's for interacting with them.

This would involve writing an integration layer for each service and probably a security manager for storing credentials to access said service (not sure if any of them let you have anonymous connections).

This is out of scope for ServerSync at the moment, it is a great idea for a project of its own though.

You could also look into free minecraft server hosting, there are a few of them around that let you configure mods.

Yeah I'll see what I can do about the server.
I'm glad you took an interest in my suggestion. Thanks!

@rheimus You could just support the webdav protocol. Many services, including Nextcloud providers, have the ability to share public webdav links. I recommend using sardine if you go this route.