I have stressed all morning regarding this minor issue.
I have x sharepoint sites, some of them are public some of them are private. I want to be able to modify the privacy settings through code, but so far I have only been able to do it manually.
I can set the field if I create the site anew, but I have not managed to do it if the site already exists.
I have also looked into: https://learn.microsoft.com/en-us/powershell/module/sharepoint-pnp/?view=sharepoint-ps, but have not found a commandlet to update this.
Answer: I finally managed to get this to work using the _api/SP.Directory.DirectorySession/Group(id) endpoint.
I could not find official documentation though, and had to do it by moniting the network traffic