Thanks for sharing! Yes, video conferencing for more than 4 is a hassle, because Nextcloud talk only supports a proprietary signalling server (“high performance backend”) which costs a fortune (starts at 4000 € for 50 users/year) The underlying problem seems to be that peer-to-peer video streaming doesn’t scale well. If you go above 4 participants, it just eats too much bandwidth. A signalling server, as I understand it, channels only the stream of the active speaker and therefore drastically reduces bandwidth consumption.
I wonder whether Apache Open Meetings or BigBlueButton are suitable for webinars/web conferences with video, but I haven’t gotten to installing it yet.