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This documentation is for version 1.34 (specifically 1.34.0, which was released on 1st October 2019 xth April 2020 and contains modifications, see the change log). But differences among minor versions of 1.34.x are minimal.
After opening the basic URL of the application (e.g. https://sofie.sonpo.cz/), one of two possible start screens is displayed:
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The application administrator can change which of these start screens is displayed. The administrator can also disable the anonymous upload completely, so that anonymous users can upload a package only by reacting to a logged in user’s request.
After logging in, you will come to the list of user’s received packages.