Operating system
The Operating System section on the Advanced settings of the Targeting area of your CTV campaigns allows you to target certain OS.
By default, all are selected.
Select/unselect any OS by clicking on the box beside each option.
Use the 'select all' checkbox to easily select all
The 'Any/No Operating system' switch will automatically select all too.
Apply OS versions
If you want to target specific Operating system versions, simply click on the switch beside 'Apply operating systems versions'.
That will deploy the selection of the ability to select minimum and maximum versions of the OS, for each of the OS.