BigBlueButton or Jitsi (we will evaluate which works well for conferencing. We have used both and they both work well but BBB might win). If you have any thoughts here, please leave a comment.
I would throw in another contender: https://meet-app.io
This is currently a few binaries/containers, but if there is interest we could compile it into a single executable which would make it easy to deploy it in a cloudron app container.