My question is: why we have to be stuck in nostalgia? Why isn’t there today a computer with modern processors and GPU which can boot to a REPL, where you can easily interface with all the HW, for example audio and video? I wanted to do something like that for the RP400. But is more difficult that it seems…
Modern hardware is too complex to understand and bootstrap for a single person even more so as a hobby project. These known unknowns can be a powerful motivation for someone who (partially) understands modern hardware to tinker with understandable systems. Some go down the retro route while others use medium to largish microcontrollers.
It’s cheaper to just outsource making the board, but I even made my own simple boards (etched using hobbyist CNC machines). I even used a bunch of surface mount parts with them.