My MX Master 3 doesn't play well with MacOS. It started after I downloaded the beta. First, my gestures and custom mappings stopped working. Steps attempted to fix:
1. Uninstall Logi Options (alpha) using un-installer
2. Rerun Logi Options+ (beta).
This led to a failure to start the backend.

1. Reinstall Logi Options and uninstall beta.
   Mappings still did not work. Prepare for clean install by uninstalling Logi Options again.

2. Upgrade OS to Big Sur

3. Get clean download from Beta site.

4. Install Beta
   Gesture button still not working at all. The custom mappings for apps works until I decide to change one. The one tested was Google Chrome and when I changed my wheel button to refresh the page, no refresh occurs.

Next Steps:
1. Attempt to uninstall logi options+ and get back on alpha to when my mouse was working correctly.

I am happy to help with the debugging process on this. I realize that a lot of this is probably a mistake in my environment somewhere. To be sane, I have Input Monitoring and Accessibility permissions given to Options+.