There's big money for whoever can identically clone the functionality of a popular computer - witness Compaq.
Is it "hard but doable by appropriately skilled modern engineers", or "impossible"?
Surely the rewards are there for whichever company can do it properly.
So why is there no proper clone of the Raspberry Pi?
Wikipedia also quotes a price range of $4.00 to $70.00 [2] for various Pi model introductory prices (they don't quote as "2020 dollars").
There is much more room for profit available to someone who is cloning a $4,455 product than there is to someone cloning a $4 to $70 product. The comparative very low price of a Pi vs. an IBM PC from 1981 likely makes it not profitable to "clone" and so no one is attempting to clone the Pi's.
Most similar boards are created with their own vision such as faster storage or more networking but at different price points. These include the PINE A64-LTS, Orange Pi 4B, or BeagleBone.
This market also includes many carrier boards for the Raspberry Pi compute module (3 or 4). For example the Turing Pi V2 mini-ITX cluster board with four Raspberry Pi CM4 modules!
Oh wait I know the answer - the price. You want it cheaper. But it's already subsidized by Broadcom so how do you think a cloner would make any money off of it?
Or are you trying to use it in a product and you need a second source? Because that way leads to doom as well.
However Broadcom didn't appear to like where/how they sourced the components and refused to sell them any more chips.
https://hackaday.com/2014/07/30/a-real-raspberry-pi-clone-no...
It would be great for industrial uses if someone made a pricier, but more readily available clone.