Managing sound and video settings during Teams meetings and calls for optimal communication
I have exact same issue, while using Teams web (Chrome or Edge), on a Mac.
I've been using Teams for more than 3 years without headphones or external microphone and no issues until last week, when my colleagues started complaining about echo problem. Teams desktop app does not have same issue.
It seems to be solved now, after changing "Noise Suppression" option from "Auto (default)" to "High", on device settings, before starting a new call; then I put it back to "Auto" and seems to be working correctly so far.