I’m running my trusty old Antec 900 with three Rosewill hotswap bays to hold 12 3.5” drives.

https://gamersnexus.net/cases/goat-antec-900-case-revisit-new-900-2026-review-benchmarks-and-thermals

https://www.newegg.com/rosewill-rsv-sata-cage-34-hard-disk-drive-cage/p/N82E16816132037

I’ve got this laying on its side currently, and I need to replace the failed top exhaust fan, but I’m sure you could come up with a rack mount option to throw it in a rack. Probably about 4u tall on its side.

You’re thinking of a desktop KVM for connecting multiple computers to one set of devices. This post is asking about network attached KVMs for providing remote access to virtually a keyboard, monitor, mouse plugged directly into a machine. This allows out of band access to things outside of the operating system - e.g. bios/efi, entering full disk encryption passwords, even pressing power/reset buttons via jumpers to motherboard headers. This type of KVM is equivalent to Lights Out Managers like LOM/DRAC in the server world.

Video games have gone this way too. Pop in disc or cartridge, go to play, forced to download updates that fix what was shipped in a broken state.