What's your opinion on https://inthelocus.com/ ? They got screen sharing without plugins. Most WebRTC-ish implementations don't have this but apparently whitelisting by Mozilla/Google is necessary to do that, so FOSS is not possible at all for screen sharing?
When I click "Share screen" I get "Screen sharing in Chrome requires installing and enabling our small extension." which attempts to install their plugin[1]. This is the same as every other WebRTC screen sharing I've used.