SMB stands for Server Message Block but on a basic level it's sharing files and folders.
Since I posted the above message I have spent many hours in que at Microsoft help on the same ticket, and at least 7 or 8 different techs. to try and fix network file sharing on my home network.
I figured, fix the network first.
In between I sought out everything I could find about SMB protocol, unfortunately most of the stuff on MS is server related, but still I learned a little from them and from some folks here as well.
For example, in Windows 10 and 11 at least, SMB 2 & 3 appears to be enabled by default. But you can also enable the earlier SMB v1 which is likely more sympatico with older Oppo's. Unfortunately it ultimately did me no good but I'm told from one person using a NAS that he uses this protocol enabled to share files with his Oppo.
So I've had some limited success with file sharing on the network but it hasn't helped the Oppo to see any files on it's network interface.
I tried something different.
Windows actually has provisions to enable NFS which is I take it is more of a Unix file system thing. Anyway I enabled it in Windows and downloaded a trial program called NFS Server.
Lo and Behold, after some back and forth with the developer in Germany, and getting my firewall setup to pass the proper ports, my Oppo was seeing folders I made available with the software! including .iso files!
So I bought the program and now am happily playing DVDA, DVD, SACD, and Blu Ray .iso files through my Oppo via the network from my pc!
Of course any other files the Oppo is capable of playing as well.
That's where it's at now, and while it sucks that I can't get the Oppo to see files/folders with simple file sharing in Windows, at least now I have a solution that works for me.