Senfcall.de is a privacy-friendly free open source video conferencing site which aims to provide an alternative to proprietary services. You can follow them at:
➡️ @senfcall (in German and English)
Their website is at https://www.senfcall.de/en
Calls are made via your web browser using the FOSS BigBlueButton system.
A newer server operated by the Mastodon gGmbH non-profit