When I arrive late at a physical meeting, I make as little fuss as possible and disrupt the meeting as little as possible. I don't stop the meeting and ask, out loud, what the topic was.
Likewise, in Zoom, if I'm late, I sit tight and listen. I don't interrupt or disrupt the meeting, out loud, by chat message to everyone, or by chat message to the hosts to ask about the readings, the format, etc. I leave the people who got there on time to enjoy the meeting.
Of course, ideally, I should be on time, too!