get a template with content so that the template can be used to create a site with content

Sounds like a job for the PnP Provisioning Engine.

You can use PowerShell or CSOM to extract a template, then apply it to another site. The PnP provisioning template can include lists and libraries as well as pages and client side components (web parts), as well as other things like permissions, groups, navigation etc. All this is configurable within the extracted PnP template.

https://docs.microsoft.com/en-us/sharepoint/dev/solution-guidance/pnp-provisioning-engine-and-the-core-library