Are you saying the burner clicks and lights when selected on at the same time as another burner but won't click and light by itself?
To what Kenmore model range and Youtube are you referring?

Usually better and easier DIY to plan on changing the spark module first, then later the ignitor. That way you at least have some assurance that two of the most troublesome parts are good before you go deeper.

It is extremely unlikely that it is the wiring harness, and it can be tested if you can find someone to loan you a multimeter. Make sure you unplug the range before you do anything. Even without a meter, you can still test the harness, and some other items, by swapping. In terms of diagnosis, when you have multiples, you swap one item from the troublesome side and see what happens. So if the right front burner ignites, but not the left front burner. if it isn't too hard, swap the two ignitors and see what happens. If the left front stops working and the right one does when you do the swap, the ignitor is bad, and you know the harness is fine. If the problem stays in the same place, then it wasn't the ignitor, but it must be something else.

Suspect the OP was watching this Youtube video which talks about the "ignitor wiring harness" (apparently how the part is cataloged).

Here is a link that might be useful: Burner that doen't click