vojta - Paul Vojta's original DEBUG, the original FreeDOS DEBUG
https://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/dos/debug/vojta/

debugx - Japheth's Debug/X, based on Vojta's DEBUG
https://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/dos/debug/debugx/

ldebug - ecm's lDebug, based on Debug/X
https://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/dos/debug/ldebug/