There's an echo or feedback in my meeting

Echo almost always comes from one specific participant who is using laptop speakers with their mic open — your voice is captured by their mic and replayed back to you. Mute everyone except the active speaker to find the source.

Permanent fix: ask the offending participant to switch to a headset, lower their speaker volume, or mute their mic when not speaking. The browser's automatic echo cancellation can't fix the round-trip echo introduced by another room's setup.