A very niche type of device that integrates a large amount of tape-based drives together, for the purpose of archival and storage. Due to their uncommon and “corporate” usage, it is hard to determine what CPU architectures and OSes are common, although it is likely that Unix-based OSes are at least somewhat prevalent.

panel computer had easy access to BIOS and I just netbooted Debian; typically runs Oracle Linux

An unexpected computer placed on a big set of tape drives. Normally, this computer controls the little cards that manage the tape drive, but it can be easily netbooted off to run some other OS, such as Debian. Also runs Doom, of course; this is what the links are demonstrating. Outside of that, the presence of a relatively full Linux distro means the onboard computer could very well function as a typical PC, outside of it's peculiar placement.

https://www.youtube.com/watch?v=vaQoD5gvIAc

https://old.reddit.com/r/itrunsdoom/comments/ezpapm/sun_storagetek_sl3000/