How do I duplicate SharePoint Teams Site?

HI, 

I am building a PMO and have set up a teams site with various lists, doc libraries, links to Planner etc.  - what I want to do is duplicate that site or use it as a template. 

Can't see a simple "copy" button nor do I have Save as Template option.  

What is the easiest way to duplicate a site ?

We are using SPO with a hub collection with sites.  No subsites. 

Thanks