This is what we're trying to do with Mathesar (https://github.com/centerofci/mathesar https://github.com/centerofci/mathesar). We probably don't meet your needs

This is what we're trying to do with Mathesar (https://github.com/centerofci/mathesar https://github.com/centerofci/mathesar). We probably don't meet your needs yet because we don't support real-time concurrent editing, but we're actively working on the project and it is early days.