Does one exist?

Inert drm means that a game installer will install a drm package (SecuROM, StarFoce, TAGES,... ) along with the game but it's never called/run by the game when you run it.

So it's harmless... but it's still dead weight and it's still there.

Define inert DRM.
Chronicles of Riddick still has traces of TAGES (or whatever its DRM was), which is obfuscated or something, and quite a few antivirus suites complain about it.
Motoracer 2 uses a crack that makes it incompatible with Linux.
Arcanum uses (or used) a scene crack to de-activate its DRM.

What about games like LLL? I do not have them on gog, but I seem to remember it had questions from the manual (mugshots of women?) are these still active?