is there an app like File Explorer for the latest iMac

You are right there, Finder is far more powerful than File Explorer. What are you attempting to do that you cannot do with Finder? Chances are you simply don't know how to use Finder or are expecting it to act just like File Explorer.

Tell your friend that there are apps which work like explorer available in the App Store, however I would encourage your friend to learn how to use Finder which is fully integrated into MacOS and has many built-in utilities. There is a lot of expert support for Finder which is invaluable.

Finder.

Finder is not remotely like the Microsoft file explorer.

I was asking for a friend who uses a PC. As there doesn’t appear to be an app that mimics File explorer I will try and point out the benefits of finder to him. Thanks for your reply.

I use File Explorer, the pro version works across local networks and most Clouds. Plus the license also pays for the iOS/iPadOS/tvOS versions. The free version is good too, ad-less. Can recommend.