I'll keep the things simple.
These flashable zips will "fix" the HDR+ capturing in GoogleCamera and the dark/greenish RAW images in camera2 apps on the Official OxygenOS 5.0 and all BETA releases after it (3 and 4 for now)
How it works:
These zips will replace/overwrite your current camera.msm8998.so (camera HAL) with the one from OxygenOS OpenBeta 2.
I did just a quick test on both apps (stock and gcam) and all looks fine.
Use on your own response, nothing is guaranteed here!
For Magisk 14.x: GDRIVE
For Magisk 15.x: (All credits to @shadowstep for updating it)
Normal flashable zip: GDRIVE
Have fun (: