I'm also running into this issue.
The problem seems to be specific to Chrome.
I'm running the latest Chrome Version 140.0.7339.81 (Official Build) (arm64)
Mac OS Sequoia 15.6.1
MacBook Pro M1 Max, 2021
My Troubleshooting:
Tested Zoom - it works
Tested Google Meet on Firefox - it works
Tested Google Meet on Microsoft Edge - it works
It seems to fail only on Google Chrome
What I tried on Chrome:
Tested on Guess Mode - Issue is reproducible
Made sure sharing permission is enabled in System Settings > Privacy & Security > Screen Recording.
I even disabled it, restarted the MacBook, and then re-enabled it, but it didn't work
Disable Hardware Acceleration for Chrome in chrome://settings/system
None of the above fixed the issue. Could this be an issue introduced in Mac OS version 15.6.1 (24G90)?