If you want to make an Amiga 2020 today you will really need something that the normal PC/Apple/phone/console does not do.
For example:
The Amiga 2020 needs: a 64 core CPU in which each core or set of cores can run a fully independent&secure version of the OS. I'm thinking switching between OS's like the Amiga workbench could switch between resolutions.
The Amiga 2020 needs of course a hardware chip that does perfect speech interpretation. None of this half/half Siri or Ok Google stuff. The local AI on chip will handle that all.
The Amiga 2020 needs a hardware chip that will control any set of VR glasses easily. The OS will of course have a graphical layout that will fully use AR and VR capabilities such that the user can do cool things with it like AR augmented desktops that exist both on computer and physically on the desk in front of you. I want to have my AR rolodex as my address book.
The Amiga 2020 needs 21st century expansion to talk to external devices. Either via 4G/5G such that computer and peripheral can always talk to each other no matter how far away they are. Or something more fancy like low power led/laser beam comms so that you just have to place the peripheral next to the computer to make them sync up.
The only thing missing is the spirit of the "future of the computer". Do not underestimate how optimistic we were at that time that computers, with their endless possibilities, would solve just about any problem in the world. The 21st century is a very different place.