I know - I just can't fix this. I use gui: https://github.com/krzysiekpiasecki/Symfonator

It came with encore/npm - im not master of it. I just learned a bit when started working with it, and the errors are just there. I dont know why. It would take alot of time to deal with it for me.

For testing You can skip that part it's only for development mode when doing something with javascript - working version works fine with just composer installation.