Thanks, M. H. Lee. I think Veinglory might be right regarding different editions needing to be differentiated according to intenral content, unfortunately. I think this may be a policy that gets overlooked or is not policed rigorously, but maybe that's not a chance worth taking. Perhaps a solution is simply to offer print versions with different covers through different POD services - e.g. KDP and Ingram Spark. Could that use the same ISBN? Or I guess it could be different ISBNs, and then it wouldn't matter if the content was the same because they have different publishers. The other option is to do limited printruns of the book and keep it as physical inventory, and then simply change the cover and do another printrun.