wp_ajax_gutenberg_signaling_server

See hook in action

See this hook used in plugins:

Select Plugingutenberg.17.0.2gutenberg.17.1.2gutenberg.17.2.3gutenberg.17.3.0gutenberg.17.4.1gutenberg.17.5.0gutenberg.17.5.2gutenberg.17.6.5gutenberg.17.7.0gutenberg.17.8.0gutenberg.17.8.2gutenberg.17.9.0gutenberg.18.2.0