Plugin, getting an entry when one of multiple category fields and/or lightswitches are not empty/turned on
If found the answer. You can use an * operator in the search query to check if a category field is not empty. So the solution in my case was:

'search' =&gt; lightswitchOne:1 OR lightswitchTwo:1 OR lightswitchThree:1 OR categoryOne:* OR categoryTwo:*