I installed it originally on a MB 5,2 and then swapped drives to the 4,1 to get it booting. Not sure, but NVRAM parameter no-compat-check could help as well. When editing the platformsupport.plist, make sure to correct the file properties (i.e. with tool "batchmod" or the terminal commands)...
Update on progress on the MB4,1: Got the latest round of beta 10.14.4 up and running also. Graphics still semi-accelerated (full frame buffer, but no OpenGL). As I have not tried the suggestion of pre-linking kernel on another machine (could need some more detailed support, newbie in this field), I´m waiting for the USB mPCIe cables to arrive. Drivers for the card already up and running ;-)
Note to
@dosdude1 : With the new self-checking patch updater tool it´s a bit of a nuisance that the older, fully working and needed audio replacement kexts are detected as "overwritten". When re-applying the patches on the MB4,1 (i.e. in combo with the nightshift patch), afterwards audio is non working. In a second step, the older audio kexts are to be re-copied again. Suggestion: Pls. add the treatment of the MB4,1 and the proper audio kexts to the data base of the patcher. That would be really welcome... ;-)
(zipped kexts added here again for your conveniency)