All versions of Windows have PS/2 drivers included with them. The only time some additional software may be needed if the keyboard has additional keys that are non-standard for example shortcut keys to a particular piece of software, which was typical of HP and Dell computers back in the late 90’s early 2000’s. Even multimedia keyboards that have volume controls and Internet keys should have no issues on Windows 11. As far as plugging a PS/2 keyboard into a USB port there are plenty of adapters for that you can get cheap, they used to include them with the keyboards and mice, but they got thrown away most of the time.
Keyboards that have got additional keys, or require extra drivers for whatever reason the drivers will be below.