Why can't i find any work of Edgar Julius Jung on digital format?

Because his his main work was translated by Alexander Jacob for a small press and costs like 150 dollars for each volume. I believe he has a few essays in the Weimar Republic Sourcebook. Additionally there is an unpublished phd by some guy who did a study about him floating around on the net if you can find it.

Written too late for public domain, too early and too niche for commercial ebooks