I tryed this version from BigKaka:
Download AGC8.4.300_V9.1 by BigKaka.
with the configuration file for Xperia 1 III and its the first that has HDRnet (not HDR+ or enhanced) active and it doesnt freeze the viewfinder and saves the file.
The problem is that it needs tweaking cause it hasn't got the correct lens settings and it's too wide from beginning on the main sensor.
Try it, tell what u think and if u think we can get something from it.
Generally on BigKaka's versions you can tweak many settings