The Screen sharing feature is highly dependent on the operating system of the device whose screen you are trying to capture.
Chrome browser used on a PC is most compatible, fully supporting screen sharing with audio.
Firefox on PC supports screen sharing, but it cannot screen share with audio.
Safari on iOS does not yet support it officially, although it does support it with the "technical builds" designed for developers. Until Apple officially supports, there isn't much I can do there easily.
Android does not support it and it is doubtful that it will in the near future.
In either case, you can use Native mobile apps to solve this problem, but the native apps created so far do not yet support screen-sharing either. Working on it though.