Meeting group chat: Turn off “[person] joined as a guest” and “[person] left” messages

Have you already tried disabling Continuous Meeting Chat? This should stop the notifications.

To enable or disable continuous meeting chat for your own use:

1. Sign in to the Zoom web portal.
2. In the navigation menu, click Settings.
3. Click the Meeting tab.
4. Under Schedule Meeting, click the Enable continuous meeting chat toggle to enable or disable it.
5. If a verification dialog displays, click Enable or Disable to verify the change.
   Note: If the option is grayed out, it has been locked at either the group or account level. You need to contact your Zoom admin.

More info here: https://support.zoom.com/hc/en/article?id=zm_kb&sysparm_article=KB0058301#:~:text=Sign%20in%20to%20the%20Zoom,to%20enable%20or%20disable%20it.