FYI all — I finally figured it out:
TLDR: moved VLC down in the selection order for inode/directory in the File Associations dialog of KDE
I had associated VLC with inode/directory in Dolphin and it either defaulted to top of list or I put it there, so it was selected by default when clicking on any “open directory” button that referenced this list. I found at least one other program doing this (the Mount and Open command that appears when inserting an SD drive).
eta: I don’t know if this is at all clear, please let me know if you have any questions.
Thank you everyone for your kind attention and efforts.