MODDED WARFARE has release an application to backport higher firmware games to 5.05, I haven’t tried this application and I don’t know how it works, but as it is from MODDED WARFARE I am sure we will see a video from him showing how to use it:
EDIT
MODDED WARFARE has already made a video that I missed:
Download v1.0:
https://mega.nz/file/HZNxSCYA#qdhFvKED4mSbOGdzJAKoHYs-klXQWEuwFH_EnkQmP-s
Source:
View The Thread Here https://playstationhax.xyz/forums/topic/6098-released-ps4-backporter-by-modded_warfare/