I downloaded it. I had to rename "Tenebra.prg" to "TENEBRA.PRG" to be able to load it easily. I used joy1 command line option to activate the SNES pad.
On level 11, 14 and 16 introductions, graphics are not the right ones. See screenshots. On level 11, unstable doorways graphics are replaced by braziers ones.
On level 14, braziers graphics are replaced by a torch man and a torch graphics.
On level 16 broken rails are replaced by torchs.
But it won't stop me. I finished this port too, minus the little graphical bugs in introductions page. I thought it could be a linux emulator bug, but I got the same display with the win64 emulator.