The furthest I was able to debug the issue is by looking at the errors spit out by:
The thing found by @Charlotte in the other topic was indeed one of the things I ran into. The code doesn't like it if you specify no create_organization_network.copy_from_network_id. Setting it to '' (empty string) doesn't work either. So I added an actual network in. But then in the end I got an error 500 which didn't give any hint as to what is happening.
The most verbose I could get was by using this piece of code instead of the original: