Read Only Admin Role

Hello,
I am looking for a way to grant access to an user as an Admin to a specific site (part of a Multisite), but disabling permissions to save or modify posts, pages and settings (to themes, site itself and plugins alike).

Basically a Read-Only Admin capabilities that grants access to any sections so that the user will be able to take vision of the status of a site, without being able to change any bit of it.

Could you suggest a way to achieve that goal? Perhaps creating a specific Role?

Thanks, kindly,
Carlo