The simplest way is to rename the original ‘Shaders’ directory in-place as something like ‘Shaders_OLD’, and just copy the new one into the Engines/UE_5.4/Engine folder.
Doing that, I personally have no crashing or compilation errors.
After doing so, I rebuilt my entire project… just ‘because’
I went into a level that had known shadowing issues, and reenabled ‘cast shadows’ on the lighting.
NO CHANGES! 
Still the same glitching, solid hard shadows with one eyes, soft edged shadows with the other, and general flicking all over the place.
So… certainly not a fix for me. And if this is the fix from the upcoming 5.4.3, then it looks like its still gonna be bugged for some time to come 