I suggest you use the “Discussion Group” in flatcam.org for an extended discussion on how to achieve your particular goal.

I did not make this video, but the way the speaker gets rid of the internal path is quite clever. The problem is that the internal and external paths are the same object. That is why you cannot select them separately in the beginning. By cutting a piece out of it (what he does with the rectangle and the “subtract” tool), the complete group of lines is broken into separate pieces. Now you can select the interior independently and delete it. He does “update geometry” several times, but this is not required.

You can also take a look at the “interiors” or “exteriors” shell commands. Those will select and create an object with just the exteriors or interiors of any geometry object. Just type “help exteriors”.

Cheers,

JP