Unix workstations might be extinct, but Linux systems are the birds to the workstation’s dinosaurs. The software environment pretty much continued as is
Due to the environments and tools being so similar, the pool of real world system administrator and end user knowledge did not have to be created from scratch. Unix User Groups soon gave way to Linux User Groups (often almost the same cadre of folks). This was essential to such a rapid transition from Unix workstations to Linux.
A raspberry pi running linux might even be faster than some of these old workstations, with better graphics to boot.
This is true, you could even run Windows 10 Pro for ARM on it if you're willing to put yourself through the grinder.
Than some. Will be nice to see some benchmarks. R-Pi 1 was not exactly flying. (R-Pi 4 is out of stock)