After installing ArcGISPro_23_167023.exe, NOT for all users, just myself, installation folder defaulted to my user directory, instead of C:\Program Files\ArcGIS\
Then, installing ArcGIS_Pro_233_168940.msp failed at every attempt, whether as a "software update" in ArcGIS Pro, or running the downloaded MSP.
First, 1304 error, followed by 2349 error.
Neither error appears in the UpdateLog.txt (attached)
Prompted to make sure I "had access to" the folder, I did indeed have access, that was not the problem.
Following tips in https://community.esri.com/discussion/create.jspa?containerType=14&containerID=2151 I turned off virus scanning and firewall, that was not the problem, either.
Reinstalled Pro "for all users", in default C:\Program Files\ArcGIS\
Patch installed without errors.