PowersHell and graph - setting SharePoint folder permissions help

Hello folks

Recently we've been playing with Powershell and having to move on to graph to do all the fancy things we want to achieve. MS forced this when they suddenly decided the MSOnline module was retired and things stopped working.

We've built a great New Team with SharePoint and including folders script. One of the things we used to do with the PNP module is set folder permission on two of the folders in a new team, making them only accessible to Owners. How the devil does one achieve this with Graph?

Any pointers would be grand.