The 24" iMac7,1 has an MDM graphics slot. I've upgraded the CPU (Intel Core 2 Duo T9500) so that using DosDude1's tool, I've gotten Mojave installed on it. If I throw in a more modern card that uses the same slot and has support in Mojave (say an AMD R9 280X MDM) think it might work? I know it wouldn't be Mac flashed. Maybe a need to manually change a kext entry to link the card to the driver? Aside from losing the splash screen (and option key function to select boot drive), could this be successful?