Glad to see that it was you who responded.
1) I'm happy to share whatever information you need from the Console to debug the Mac Remote Desktop client. I wouldn't know what questions to ask Apple or even who to call. You must have a developer who interacts with Apple. I suspect that thus could be a problem for others who don't know how to get into Console or to find informative messages, given the message volume.
Could I persuade Microsoft to debug its Mac client?
2) There is no error message wen the RDP session fails, just a frozen screen. That's why I dug into the Console. I ran 10.5.1 beta for a day and noticed that it spews messages, so that kind of logging is available. I just excerpted the console log into "2020-12-23 12-34 Console event log excerpt filtered for remote desktop.docx", if it would be helpful to see what log entries Remote Desktop is generating, as well as the OS service messages. I see that RemoteDesktop set a breakpoint at SLSLogBreak just now, which I haven't seen before.
3) There are several logs in Event Viewer. In the Windows Logs - Security, I can find Audit Success entries ID 4672 Special Logon at times that match the Mac Console for runningboardd Acquiring an assertion, but that log doesn't have entries that match the Console time stamps for Invalidating Assertion.
Neither the Event Viewer Windows Logs - Application nor - System had any entries for Remote Desktop.
The Event Viewer Applications and Services Logs allowed me to create a Remote Desktop New View. One message that is a red exclamation point error that occurred ever 40 seconds for several minutes says "'Event 227, RemoteDesktopServices-RdpCoreTS Failed CreateVirtualChannel call on this Connections Stack' in CUMRDPConnection::CreateVirtualChannel at 2958 err=[0x80004005]"
There also is a warning, "Event 105, RemoteDesktopService-RdpCore-TS"
Does that provide what you wanted from the W10 logs?
Thanks, Ernie Cell 415-902-6112