In Spaces, if you have the full screen open for a video call, there is no indication that any chat activity is occuring. Some members of the call may be having an active chat, while others don't know it's happening.
I suggest an icon at the bottom of the screen alongside Hang Up, Share, Allow Camera, etc. that is labeled "Chat" and shows a red badge indicating there is something new in chat. This can prompt meeting participants to check the chat.