Yabai requires disabling System Integrity Protection (SIP). The Github utility WhichSpace (I know you know this, Jim) does not notify, but it does track which Desktop Space is active and can report that via AppleScript.
tell application ¬
"System Events" to tell process ¬
"WhichSpace" to set newWhichSpaceNum to (title of menu bar items of menu bar 1)
return newWhichSpaceNum
Also see this thread and its links for more info on WhichSpace: