I'm going to retract the "sighted help required" for running the COM registration fixing tool with a silent NVDA main menu, at least if you trust your own typing skills. The command sequence for this is:
NVDA + N, T, R, Enter
And that Enter is necessary to kick it off. It remains an open question as to whether the dialog would talk for that, too. If it doesn't, then hitting Enter again activates the default Yes button for the question, "Do you want to run . . .?" I'd hope at that point, when the UAC dialog pops up you'll have speech, but if not hitting ALT + Y will allow the COM Registration Fixing Tool to run. It does it's thing and then, a final dialog comes up saying that the COM registration fixing tool is complete, with the only button being the OK button. If there's still no speech by that time, hit Enter again. So, the short version, after the above command sequence, for as long as silence persists, the following would need to be hit, in order, with a slight pause after each is hit:
Enter (Activates Yes button for NVDA Com Registration Fixing Tool question)
ALT + Y (Activates Yes button for Windows UAC for tool to run)
Enter (OK button for tool saying it's done)
Brian - Windows 10, 64-Bit, Version 21H1, Build 19043
Nothing in all the world is more dangerous than sincere ignorance and conscientious stupidity.
~Martin Luther King, Jr.