Checked your thread for what you need for a bug report, so I've tried include all that you need incase you are interested in getting your GCam up and running on the Xperia 5 II.
Phone: Xperia 5 II, stock rom, no fixes
Camera2 Test and logcat attached of the crash.
Hi, i downloaded and tested it: IMHO Sony Photo Pro app gives better results
my 2 cents
I find a webpage of GCam for Xperia 5 II. https://www.cyanogenmods.org/google-camera-xperia-5-ii/
I tried it but all crashed, maybe because my phone is China Edition. You can try it.
Are you running this version?
On my 5-2 this GCam is semi-working. It takes photo on 16 and 70 mm module. Sometimes you can enter the menu using the button LIB from the tenth time.
(If the image from the camera is visible and falls out, move the slider to the video and choose a different camera).
Perhaps someone can make this version work and run the main photo module (it works in the video).