I have not been able to find a way to mount in the external card slot an sd card formatted (under linux) with an ext4 file system on it. I have a rooted P600 tablet running kitkat, with the external sd card fix. I'd be grateful to learn it's just plain impossible, or to have a pointer to a solution.
XDA Developers was founded by developers, for developers. It is now a valuable resource for people who want to make the most of their mobile devices, from customizing the look and feel to adding new functionality. Are you a developer?