I have Finder preferences set to "Open folders in tabs instead of windows", but when I open a finder window I do not see any tabs, only folders and when I double click on a folder it opens in a new window.
Finder used to just open the folder in the same window revealing the contents of the folder thereby allowing you to navigate to the file that you would like to open in the same window and then once you found the file of interest and double clicked that file, it opened.
I would like to get back to that version of Finder.
If I open Finder using Go to folder and choose the Macintosh HD then the finder window opens with tabs and I can then navigate to the file of interest.
On the other hand, if I Go to Home, the finder window opens without tabs and now any combination of double clicks opens a new finder window.
I can live with this, I just hope I do not have some adware or something similar that has changed the Finder ... ummmm ... I suppose there is nothing to worry about?