Mattermost
Mattermost is an online communication and collaboration platform that serves as an open-source, self-hostable alternative to platforms like Slack and Teams.
BigBlueButton
BigBlueButton is a virtual classroom software for synchronous discussions or lectures between students and instructors. Emphasis is placed on real-time communication. Sessions can easily be recorded and made available; however, uploading may take several hours or even days depending on the size of the recording. If you are looking for a screen/webcam recording and video platform that integrates into Moodle, refer to our Kaltura guide.