Codeigniter 4 in intranet

Intranet/Extranet/Internet from a networking perspective are essentially all different portions of the same network nowadays (where an Intranet or Extranet is simply 'dark' (hidden) to most global users). Sure, there are some differences, particularly when it comes to security concessions/permissions and what one has direct control over (or has to provide oneself, if desired), but from a networking protocol perspective petty much everything is (or can be) the same.

So CI is perfectly suited to any of these- it wouldn't really know, or care about any difference (though, of course it (or Apache/AN Other webserver) couldn't make use of services on the Internet that were blocked in your Intranet- for example: a Certification Authority for HTTPS).