The HRI2021 proceedings are available from the ACM digital library.
Full program schedule: https://humanrobotinteraction.org/2021/schedule/
Companion Proceedings (alt.HRI, Demonstrations, Late-Breaking Reports, Pioneers Workshop, Student Design Competitions, Video Presentations, Workshop Summaries):
Daniel Rea (University of New Brunswick, Canada; and Kyoto University, Japan)
Wafa Johal (University of New South Wales, Australia)