Thunderbird has introduced Appointment, a free and open-source appointment scheduling tool to rival Calendly and similar tools. It simplifies meeting coordination across time zones by allowing users to share their availability. Currently in closed beta, it adheres to Thunderbird's values of privacy, openness, and transparency.
https://alternativeto.net/news/2024/8/thunderbird-launches-appointment-a-free-and-open-source-appointment-scheduling-tool/