The human referee should be able to concentrate on the game. People yelling at him is not helpful, nor productive.
Each team should get a communication flag, to request both timeouts and challenges, similar to the flags for robot interchange in 2019.
The human referee has to acknowledge the communication flag. Any other communication, yelling, challenges, gesturing will be unsporting behavior: 1 warning and then red card(s).
From the rule changes proposal: