Some recent testing I have been doing has indicated that the Sony SLog3 IDT in Resolve is specifically S-Log3/S-Gamut3, not the more commonly used S-Gamut3.Cine. I have reported this to the Resolve team, but some people may need a stop-gap.
For those who can write their own DCTL, you can create an S-Log3/S-Gamut3.Cine IDT relatively easily. But for those who can’t, I have created one which I am selling for only $30. Contact me by email – nick [at] antlerpost [dot] com.
I have not tested with a wide variety of footage, but have found that it also works on F65 RAW footage shot with the camera set to S-Log3/S-Gamut3.Cine, where Resolve’s built in Sony RAW IDT does not match the result from other implementations.