For the conference website, we employed Indico (www.getindico.io), an OSS conference organization software, which proved to be a powerful tool in the conference's organization. Indico provided a registration interface, an abstract submission review platform, allowed for sending out mass emails to all participants, and provided an ordered timetable for the conference. Thus, we consider it a fitting platform for all kinds of online meetings, erasing the need for external services such as Google Forms. In addition, one could create surveys directly on the platform, allowing for centralized and facile acquisition of participants' feedback. As a digital substitution of coffee breaks, we implemented an instance of Mattermost (), an OSS chat service in which people can either communicate directly with each other or group-chat in different "channels". While we used Mattermost for our poster session and post-plenary-session discussions (vide infra), we also additionally provided one central channel for socializing and one for technical support. We envisioned that people could have "digital coffee breaks" there and discuss on-and off-topic matters. For the talks, we employed Zoom, as it is among the most used platforms during the current Covid-19 crisis and we had a Zoom Pro licence made available from the Friedrich Schiller University Jena. While we also tested an OSS alternative, Jitsi, we encountered insurmountable technical challenges. In general, the predominant use of OSS for the organization enabled CYSS to stay free from proprietary third-party services, which are either prohibitively costly (often up to 1000 € per conference) or are problematic in their use of participant data. To run Indico and Mattermost, a cheap server (60 € per year) was more than enough to accomodate the needs of CYSS. Using OSS for video conferencing, on the other hand, proved much more difficult. While Zoom has been criticized for its poor data privacy, it is much more costly to run a video conferencing system due to excessive bandwidth requirements for higher participant numbers. Even a generously equipped server with 1 Gbit/s bandwidth will only accommodate ca. 50 participants with video simultaneously and the requirements scale superlinearly with the number of participants. This makes the use of OSS for large scale video conferencing cost prohibitive and cannot be solved on a single conference level. DFNconf (), which was used for the digital poster presentation (vide infra), is similarly to Zoom not open and restricted to members of German research institutions. An additional hurdle in using OSS systems is that they need to be set up and configured by the organizers themselves. While this has become much easier in the last years, due to the availability of virtual servers and very good tutorials for Indico and Mattermost, it still requires a level of familiarity with server infrastructure and web-hosting. This requires at least one member of the organizing committee with experience in these fields.