Dear teachers,

Would you say that "how" in the following sentences is a subordinating conjunction or an adverb?

I don't understand how (1) he could behave this way / (2) how this machine works.

This is how I make a vegetable soup.
Tell me how to get there.
Do you remember how you and I planned to live in Venice?
This is how things happen.

Thank you in advance.
I wish you all a happy new year.