Just now I tried the ubuntu man page and found not all commands are Rpi buster compatible.  For example, "orca --gui-setup" does not work, but "orca -s" already goes to gui setup mode, and I can start selecting the orca modifying keys etc.  One problem is that I have no experience in using screen reader, so I found too many technical terms I don't understand.  I think I need to go back to the following intro section: "Gnome Orca Wiki Documentation Page":
https://wiki.gnome.org/action/show/Projects/Orca?action=show&redirect=Orca.  I also found that I know too little about accessible technology to understand the screen reader subject.  So I have started reading prerequisite references, including the following by PEAT: What is Accessibility? - PEAT (Partnership on Employment and Accessible Technology) https://www.peatworks.org/get-started.  So I will stall learning orca for a while and dig down to the basics.  See you later.  Cheers.