Inspired by the recent PATA discussion, it occurred to me that deciding whether SCSI was on topic or not would be a highly relevant point to consider. SCSI has been used in machines since the 1980s, but is technically still available, although its usages have really retreated to the fringes of computing. (SCSI protocols survive in modern operating systems, but the hardware is relatively uncommonly found.)
That all having been said, although I can hook up a SCSI hard disk to my 1985 Amiga, I can also put a SCSI controller card in a modern PC and run that same hard disk under modern Linux or BSD, and probably Windows 10 too depending on the SCSI controller I use.
My instinct is that SCSI is so peripheral (pardon the pun) in the modern computing word that for all intents and purposes, it is retro, but let's talk about it.