Can I do something for allowing peers join to room without microphone, or without permission?
Yes, you can. May I know why do you think that requesting microphone is mandatory for receiving audio/video from others? Where in the documentation have you read that?
You can check it on demo, if you don’t allow permission for microphone, you can’t join the room http://joxi.ru/eAO9Og1T9R6GVm
Oh, I’m sorry, but the demo is just a demo. It must NOT cover all your use cases and the use cases of all the others. Implement what you need instead of assuming that the demo is the only way to go.