Go to ...UsersDocumentsMy GamesSid Meier's Civilization 6
Then open "UserOptions.txt"
After that go to "line 60" then change "AutoUnitCycle 1" to "AutoUnitCycle 0"
Save the file "UserOptions.txt"
Once you are all done then save (Ctrl + S)

Now you are all set to enjoy the Civilization 6 game without Unit Auto Cycle.