What kind of cloud sharing are you thinking of @claire? If you want to make this kind of collaboration easy, there aren’t too many collaborative cloud environments which would offer you the kind of control that you need.
Imagine if you just share a document and multiple users start to edit it in the same section. If you’re just sharing the file rather than allowing multiple users to edit it simultaneously, then Onyx would have to collect all of the changes and find a way to combine the changes even in the case where they were made to the same section. The problem is Onyx is not in a position to really evaluate the quality of the English content (as evidenced by the current state of the manual), so how are the best submissions determined?
Any user should have the possibility to comment on proposed changes and, sometimes after a good amount of back and forth discussion with other users who have strong opinions about the change, a final version should be agreed upon and merged into the official document.
The problem is that efficient collaboration where Onyx has final control, but the changes can be debated, or the overlapping changes reconciled is not something you can easily achieve with a simple cloud file share.
GitHub (or similar version control environments like GitLab, for example) is especially built to support a multi-user collaborative workflow, with minimal effort. With most alternatives that I can think of, you end up creating more work for yourself than it’s worth.
Google Docs could probably be used for this as well, but my guess is that your resistance to using platforms such as GitHub could be due to reasons of accessibility from mainland China. I’m not sure if Google Docs is more available in that sense. In any case, I’m curious to see what you are proposing.