I have one report of issues with Sonoma, but there are hundreds of people already using Keyboard Maestro without reported issues, including several posts on the forum.
So currently I have no reason to believe there are any issues with Keyboard Maestro on Sonoma in general, and more likely the reported issue is with the particular user, but the jury is still out as Sonoma is still very new.
I have not tested Keyboard Maestro on Sonoma and likely wont while it remains in beta unless I hear of issues.