I was doing something similar just the other day and came across sqlite-s3vfs[0]. It is likewise a SQLite VFS that translates IO to S3 api calls. However, that project is only for python and seemingly abandoned. Additionally, if you want more than one writer, you'd have to coordinate that yourself, afaik.

[0]: https://pypi.org/project/sqlite-s3vfs/

Author here. The VFS support right now is currently read only so it's useful for something more like a shared cache of data.