i'm typing that post with the virtual kb having suddenly lost my physical & wired one (Dell SK-8135) under windows 10 21H1 build 19043.1165.
It works fine during boot sequence (i can enter bios setup), or with other computers running the same win 10 build. It is still recognized as a usb hub having 2 integrated usb slots.
Another kb, included wireless one (thru a 2.4 GHz usb dongle) is not running (but is shown within the media ejection icon).
Using devmgmt, NO keyboards category appears!!!
None keyboard works in safe mode or after clean boot.
Rollback to previous restore point, boot in winRE + custom install don't solve that ... issue
ANY HELP WELCOME before reformat + reinstall from scratch...