looking for video conferencing FOSS (client and server)

i am wanting to run a simple video or audio-only conferencing setup on my own server (Ubuntu 18.04 LTS soon to be 20.04) and clients (Ubuntu or Xubuntu). or better yet, simply work in Firefox when it loads the right page. buildable source is a requirement for the Linux software. optional Windows versions do not have to have source (i won't be using these). if it can do multi-user kind like Zoom, that's great but not essential. end-to-end encryption in 2-user mode. client-to-server encryption in multi-user mode. use the latest SSL/TLS.