The Greek Computer Society (GCS/ΕΠΥ), the Department of Informatics & Computer Engineering of University of West Attica, the Harokopio University, and the University of Piraeus organised the 24th Pan-Hellenic Conference on Informatics (PCI 2020) in Athens, Greece, from 20 to 22 November 2020. To limit the spread of COVID-19, the conference scheduled to be held as a Digital-conference. During this conference, our partners from HUA presented the work titled “Online federated learning with imbalanced class distribution”.