The gray question mark indicates it’s working on your end, you must use the correct image specification provided in OPDoes this work above Atmosphere 0.16.2?
I disabled all of my sysmodules besides this one, tried both 0.17.1/0.18.0 and got a black screen after the switch icon was displayed. (Using the 0-16-X_Fix zip build provided).
I also tried building the latest commit from the repo (with FEAT_NSAM_CONTROL and TOGL_LOGGING) and running it from 0.17.1/0.18.0. while I did manage to boot to the home menu with my build it only displayed a gray question mark for the game I was overriding. (And unfortunately did not produce a log)